My players are in a big city and will be splitting up to do their shopping, training, whatever.
I want them to each be followed home by a "fragment" of said creature and when they reach home thinking they're going to be fighting 4 separate guys the fragments meld together to form a larger threat.
I'm sure this can be done with simulacrum and other spells but is there a creature that can do it naturally?
Oh CR doesn't really matter, I just want it to happen at some point even if its going to be way later.
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Nine lantern archons can combine into a bigger version. That's the only one similar to what you want I could remember off the top of my head (although that's multiple creatures combining into one rather than one creature splitting up), but there are probably others.
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Have you ever heard of Sagiro's Story Hour about Abernathy's Company. They fought a pack of normal wolves and every time they killed one the rest would grow bigger. Eventually when there was only one left they had to fight a big bad werewolf.
Pick a favourite monster and just do that.
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Some oozes split when hit with slashing and piercing weapons.
You could perhaps pull off the opposite, and have the already-split oozes reform back into one big blob with lots of hp. For added effect, hold off on letting the big one reform until they've had a chance to fight and defeat one or two of the smaller ooze fragments. That way they can get used to the half-hp monsters first, before you bring on the big one.
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Voltron? :p. AND I'LL FORM THE HEAD!!
I think there was an elemental that could do that in 3.5, but it had a pretty high CR.
Would an ooze be intelligent enough to handle that function?
First question, how do you keep them from having 4 separate 1 on 1 battles?
If you tell them "something is following you" most people I've gamed with will try to get a look at it, figure out what it is, and if they figure out it seems like some kind of monster, they'll often arrange to ambush and kill it on the spot. Alone. They wouldn't go back to the group unless they thought they couldn't beat it alone.
If they already know that their group is separated around town shopping or whatever, then I doubt they'll go back to their "home" for fear that they will be all alone there when the monster catches them. They will probably need to go to the sheriff or to a temple or something to get NPC help fighting it if they think they can't do it alone and they're not sure the rest of the group is "home".
I'm not sure how to pull this off, to have them in 4 different places, each one discovers he's being followed, and each one decides to go home with the thing still following him.
Next question, if it is so dangerous that all 4 of them decide they need help (too dangerous to fight it alone), and you manage to get all of them together at their "home", how can they fight four of these things at once without dying? And if it combines into something even more dangerous than the 4 parts, isn't going to be even more deadly?
That might not be clear, so let's use an obvious example. If they're all level 4 and suddenly they each realize they're being followed by a troll (CR 5). Each of them is pretty sure that a troll could kill them alone, which is probably true, so they head "home" and now they are all together, but fighting 4 trolls. Those 4 trolls are going to TPK the group. And if they can magically transform into something even scarier than 4 trolls, say, into an Advanced Troll with 4 levels of barbarian (CR 10, I picked that because it's one CR higher than four trolls), then it's just more certainly going to be a TPK.
Third question, if you avoid those traps and reverse it, say, by using one Advanced Troll (CR 6), but having it's arms and legs come off and turn into little trolls to follow them around the city, what CR do you make the little trolls? If they're CR 5 (normal troll) then the PCs won't stand and fight them alone, but when they all get together, those trolls should fight separately - combining them into one Advanced Troll just makes them weaker - not an impressive thing for a monster to weaken itself with it's own special ability. Even if those trolls were Young (CR4), turning into a single CR 6 Advanced Troll is much weaker than fighting separately. Those little trolls would have to be about CR2 for them to combine into a CR6 fight and call it an equal trade, but then we get back to the first question, most 4th level characters wouldn't be so afraid of a CR2 enemy and they would probably just kill it on the street.
So what you need is:
1. A small fragment monster that looks super scary so none of them dare fight it.
2. Some reason that none of them get NPC help.
3. Some reason that they all instinctively know to go "home" even though they're pretty sure that none of their adventuring friends are there right now.
4. A combined monster that is tougher than all the fragments separately (or else why would it bother to combine) but still not too tough for the group to fight.
If you can put all that together, then I would say create your own monster. Have it be a living swarm of some kind, like an ogre-sized swarm of scorpions or centipedes or something, and then when it combines, it becomes a huge (fire giant sized) swarm of the same stuff. It can walk around like an ogre or a giant, make slam attacks, etc. Maybe make the individual fragments be 2 CR lower than the PCs and the combined form about 3 CR above the PCs - that way the combined form is 1 CR more than the group of fragments, still within the range of a dangerous encounter but not TPK when it's combined, but maybe just scary enough as a fragment that none of them will try to fight it alone.
First: I was considering something that's somewhat easy to fight but difficult to kill, something that regenerates possibly so that it continues to stalk them even if they defeat it. Or something with really high stealth or a vanish type ability so that the players might only get fringe glimpses of it.
I can also see this as a slowly escalating event along the lines of:
Day 1: Player 1 is stalked and "kills" the fragment.
Day 2: Player 2 reports seeing a something that seems really similar
Day 3: Players 3/4 also encounters creatures.
Day 4: Players hatch plan to lure out stalkers leading to the fragments gathering at the home.
My players will be in a city that while not openly hostile definitely encourages the PCs to keep as low a profile as possible and as such I believe the players will try to avoid fighting in any area they don't feel "safe".
The first Scarred Lands Creature Collection had the Feral - a creature with one soul split between multiple bodies. Every time you killed one, each of the others gained a hit die and other stat increases, until there was just one really powerful one left.
The great thing about this is that if one of your players does confront and kill their stalker, the others will see theirs get stronger.
You might have to tweak the stats for your party's level (the standard Feral pack was, IIRC, 15 2-HD monsters, meaning that the final version would end up as 16HD. If you start with a pack size of 4 then obviously the ability range will be that much smaller).
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How about a doppleganger so that they are followed by different people or creatures and from time to time you ask for an off the wall perception roll which if, they make it, they notice the tail (but it's different then the last time) and if they don't, they get nothing. And let them make the roll so they know.
Closest Pathfinder monster I can think of is a fairly high-CR creature in Distant Worlds. The creatures combine to evolve new forms for solving problems.
My recommendation is a variant on several different ideas people have said here: repaint and tweak an existing monster.
This is going to be a complicated thing to talk about, so I'm going to break it up across multiple posts, starting with this one, in which I place lots of links and address the first question.
I'm going to be dropping an awful lot of links here, and this series of posts are going to be huge, so I'm also going to divide each post up with spoiler tags.
Let's get some links, first.
* lantern archons combine and black puddings split
* doppelgangers are shapeshifters
* shadows and greater shadows show advanced versions of the same creature (as does the advanced template
* rakshasa display a combination of guile, trickery, and cruelty in their fluff, and their mechanics are built to reflect this (a list of all of the types, if you like)
* and, of course, trolls display regeneration (though you may want to use rock trolls, depending on the kind of creature and the situations you're using.
So... how can we use all of this?
Let's find out!
We'll take on combination-type stuff first.
Four <fusion monsters> can fuse together as a full-round action, becoming a single Large entity that is more powerful than the individual <fusion monsters> that make up its parts. Looking like a <insert description here>*, the gestalt has all the powers and abilities of a Large <insert creature here>** plus the following: <insert abilities here>***. The <fusion monsters> can remain in this form for <insert time-length here>****. When the gestalt separates back into individual <fusion monsters>, its remaining hit points are divided evenly among them; if it had less than 4 hit points, some of the component <fusion monsters> die when the gestalt ends.
*
*****
****
There's a lot that can be done with the generic template I noted above.
Gluttony's good idea about a reverse Split could be interesting too (each creature fusing together when "X event" occurs). Let's look at that ability as it applies to at least one creature, the black pudding.
Slashing and piercing weapons deal no damage to a black pudding. Instead, the creature splits into two identical puddings, each with half of the original's current hit points (round down). A pudding with 10 hit points or less cannot be further split and dies if reduced to 0 hit points.
Hm. A bit difficult to reverse engineer... but what if we don't cling so tightly to the basic mechanic or even flavor above?
<insert one or two damage types here> deals no damage to a <fusion monster>. Instead, the creature is driven back into another adjacent <fusion monster> and fuses into one identical but larger <fusion monster>, with the combined current hit points* each had before the forced combination. A <fusion creature> with more than <insert value here> hit points or more** cannot be fused and dies if reduced to 0 hit points.
*
**So that's an interesting framework for the ability. It's rough around the edges and will need some polishing and to answer some questions (like, "What happens if they're subject to that damage type and nothing is near them? Or, "How many fusions creates a more powerful creature?" and so on), but it's definitely a decent place to start.
One interesting thing is that the Shared Essence ability (which might need to be (Su) instead of (Ex) like the original Split) is that it's not actually incompatible with the Gestalt ability noted above. One method of answering some of my questions could be noting that "More than <insert # here>* of <fusion monsters> cannot be combined. Otherwise, this behaves like the Gestalt ability." That would certainly take care of a lot of (though not all) unknowns.
*
Now, one trouble spot might be the "combined current hp total" mechanic above. What if they're all at maximum hp and the combined creature's HD isn't potent enough to have all those hit points? There are a few ways of handling this.
- First: it doesn't necessarily matter. Since they evenly split their hp when the gestalt ends, that means that if they go in with maximum, they leave with maximum (unless they've taken damage). So you could just run them that way. This makes the fusion monsters seem like multiple little normally-individual creatures that temporarily combine into a bigger one.
- Second: you could have a hp "ceiling". In this interpretation, the fused creature can't have more hp than it's maximum, and thus, even if they take no damage, they exit the gestalt with less-than-maximum hit points. How to determine that maximum is up to you (usually the normal way, but you might consider max hp per hit dice or not, at your option). This makes the fusion monster seem like a normally-singular creature that (painfully) divides itself up into smaller, individually weaker creatures that are useful for other purposes.
- Third: something of a compromise between the first and second, is that you could a hp "ceiling" for maximum hp, but keep all hit points gained "on top" of the ceiling be temporary hit points that the combined monster can't get back.
- Fourth: related to the second, is that you could have an arbitrarily low "ceiling" on the little monsters, effectively forcing them to have a maximum equal to 1/4 (possibly rounded down) the big monster's hit points (which are determined normally). In this case, the little fusion monsters are definitely only projections of the big fusion monster, at least according to mechanics.
The last option, though it's not directly displayed anywhere in the rules that I know of, is the "kill it, and it get's better", like what Reebo Kesh noted. The fact that it doesn't exist has never stopped me before, so let's get cracking!
I'm going to be basing it off the Feed and Consume Life abilities they each have. Let's look at those now.
Once per month, a barghest can devour a nonevil humanoid's corpse as a full-round action to gain a growth point. It gains a bonus equal to its growth point total on attack rolls, CMB rolls, saving throws, and skill checks. Its maximum hit points increase by 5 for each growth point it gains. For every 2 growth points, a barghest's caster level for its spell-like abilities and its CR increase by +1. When a barghest reaches 4 growth points, it sheds its skin and becomes a greater barghest, losing all of its growth points (and bonuses) but gaining the stats presented on the page for a greater barghest.
When a nabasu creates a ghoul with its gaze attack, it gains a growth point. It gains a bonus equal to its growth point total on attack rolls, CMB rolls, saving throws, caster level checks, and skill checks. Its maximum hit points increase by 10 for each growth point, and its caster level for spell-like abilities increases by 1. For every 2 growth points, its natural armor bonus, SR, and CR increase by 1. Every time it gains a growth point it makes a DC 30 caster level check—success indicates it matures (gaining both the advanced and the giant simple templates) and plane shifts to the Abyss in a burst of smoke. A nabasu can have a maximum of 20 growth points—it automatically matures if it has not done so already when it reaches 20 growth points.
Well. you can probably see where I'm going with this. So let's do it.
When a <fusion monster> is killed, all other fusion* monsters it is linked to gain a growth point. Each gains a bonus equal to the growth point total on attack rolls, CMB rolls, saving throws, and skill checks. Their maximum hit points increase by 5 for each growth point it gains. For every 2 growth points, a <fusion monster>'s caster level for its spell-like abilities** and its CR increase by +1. When a <fusion monster> reaches 4* growth points, it becomes a <fused fusion monster>, losing all of its growth points (and bonuses) but gaining the stats presented on the page for a <fused fusion monster>.
*
**Well that was actually easier than I thought it would be. :)
One of the interesting things about the 'Gestalt', 'Shared Essence', and 'Strike Me Down...' abilities is that they aren't mutually exclusive. I pointed out under 'Shared Essence' how it could work in conjunction with 'Gestalt', but 'Gestalt' (and thus 'Shared Essence') could work just as well with 'Strike Me Down...', as both reference a different stat block as the new base. Simply point the 'Strike Me Down...' and 'Gestalt' abilities at the same alternate statblock.
Now, I refer a lot to the "<fusion monster>" in this post. But... what is a "<fusion monster>"? Frankly... we don't know yet! That's why it's the "<fusion monster>" instead of it's proper name!
Once we do have a proper name, however, we can search/replace all the instances of "<fusion monster>" with the proper name that we've come up with for the final creature.
Anyway, that's it for this post. The next one should be somewhat shorter. I think I'm going to discuss effective immortality and hopefully explain why the PCs might want to kill it in their home (beyond just wanting to keep it a low profile).
EDIT: it might take me a bit, though, as I'm thinking of taking a brief break. This one post took me an hour. :)
Here's a thought, take a page from "Army of Darkness." Have miniature NPC creatures with a "hive mind" so to speak that combine either into a solo powerful being, or use a swarm-type creature such as a Worm that Walks.
It would be hilarious to imagine several miniature evil Valeros duplicates torturing him... ;) only to form a Dark Valeros commanding a horde of skeletons...
I have to watch that movie now!
The Pale :)
Here's a thought, take a page from "Army of Darkness." Have miniature NPC creatures with a "hive mind" so to speak that combine either into a solo powerful being, or use a swarm-type creature such as a Worm that Walks.
It would be hilarious to imagine several miniature evil Valeros duplicates torturing him... ;) only to form a Dark Valeros commanding a horde of skeletons...
I have to watch that movie now!
The Pale :)
A nice way to apply the mechanics up above. :D
Alright, so, now that I've had a few minutes, let's look at why the PCs may want to kill it in their own home and how to make sure they don't eliminate it forever out in the streets.
While the PF version of Flaming Skull is weak, it's predecessor in 3.5 was quite sentient and potent had the following ability:
A destroyed flameskull rejuvinates at its full normal hit points in 1 hour, even if smashed to pieces. To prevent the rejuvenation, its remains must be sprinkled with holy water or subjected to the dispel magic, dispel evil, or remove curse spell. The flameskull's caster level is 14th for the purpose of the dispel check.
It also had low-grade fast healing.
That's a pretty decent starting point.
What do trolls and rock trolls have to do with this? Well, regeneration is the obvious answer. But more than that, really, they have much to suggest about alternate ways of killing something forever. Perhaps just as important is the eternal template, which is pretty much the PF-rules-equivalent on how to create something like a flameskull above. Let's take a look at it's ability.
An eternal creature cannot be permanently killed or destroyed. If killed, turned into an undead, polymorphed, petrified, burned, or otherwise destroyed, it returns to life and normal well-being 2d6 minutes later (even if disintegrated), gaining benefits similar to a true resurrection coupled with a heal. If the location of its body has become hazardous enough to kill it instantly, when the immortal creature returns to life it teleports to the closest safe space. Eternal creatures do not age, eat, sleep, or need to breathe, and they are immune to magic versions of those effects.
The downside of being immortal is an inability to grow and change. The eternal creature never gains any levels or Hit Dice. The effects of being eternal cannot be overcome with even a wish spell. Unless the eternal creature has a special weakness (see above), only the direct intervention of a deity can overcome the eternal status.
Okay, well, that's a decent starting point, but let's look at tweaking it a bit. 2d6 minutes is a decent period of time, but it's actually a little to easily accidentally discovered for my tastes. Instead, much like the flame skull ability, I'm going to suggest they have a very similar ability, modified as follows:
A Returning creature cannot be permanently killed or destroyed. If killed, turned into an undead, polymorphed, petrified, burned, or otherwise destroyed, it returns to life and normal well-being 2d6 hours later (even if disintegrated), gaining benefits similar to a true resurrection coupled with a heal. If the location of its body has become hazardous enough to kill it instantly, when the immortal creature returns to life it teleports to the closest safe space.
The downside of being nearly immortal is a difficulty growing and changing. A returning creature requires four times the normal experience points to gain levels or hit dice. The effects of being Returning cannot be overcome except with the most powerful magic, or by using the Returning creature's special weakness (see below).
Not bad, but it still references a weakness that we haven't crafted yet. Since we're designing a new creature, let's just write in the weakness to the ability. Normally it would be it's own thing, but, you know, it's a little easier here.
A Returning creature cannot be permanently killed or destroyed. If killed, turned into an undead, polymorphed, petrified, burned, or otherwise destroyed, it returns to life and normal well-being 2d6 hours later (even if disintegrated), gaining benefits similar to a true resurrection coupled with a heal. If the location of its body has become hazardous enough to kill it instantly, when the immortal creature returns to life it teleports to the closest safe space.
The downside of being nearly immortal is a difficulty growing and changing. A returning creature requires four times the normal experience points to gain levels or hit dice. The effects of being Returning cannot be overcome except with the most powerful magic, or by using the Returning creature's special weakness (see below).
If tricked into a sacred area (such as a temple, a sacred grave yard, an area under the effects of consecrate or hallow, or something else similar sacred) the Returning property is suppressed until the creature is destroyed. After this, it can be removed from a destroyed Returning creature with sprinkled with holy water or subjected to the dispel magic, dispel evil, or remove curse spell. The Returning creature's caster level is <insert appropriate number here> for the purpose of the dispel check.
The creature is clever enough to avoid being in the area of normal churches, graveyards, or temples, and won't enter such areas normally.
If you add something like a "regeneration 1/acid, fire, or cold iron" you've actually got a pretty nasty critter on your hands. This regeneration could also be shut off in situations similar to the above.
However, how powerful is this creature, really? The eternal template (which is actually more potent than the ability I show here) grants a +2 to the creature's CR. I'd stick this one at about a +1, but you could rule it's a +2, if you like.
Now, what does this have to do with rock trolls?
A rock troll that is exposed to natural sunlight is staggered and must make a DC 20 Fortitude save each round to resist permanently turning to stone. A stone to flesh spell (or similar effect) restores a petrified rock troll, but if it remains exposed to sunlight, it must immediately start making new Fortitude saves to avoid petrification. Spells like sunbeam or sunburst that create powerful natural sunlight cannot petrify a rock troll, but the troll is staggered for 1d4 rounds after being exposed to such an effect.
A weakness. Installing some additional weakness could make it less potent enough to keep it more or less in line with it's normal power level. Of course, you don't have to add that weakness, and the actual weakness itself depends entirely on the type of creature it is (which we've yet to establish).
In any event, the Returning property would give a pretty solid reason for the PCs to want to create a sacred place that wouldn't be expected. Since they can't do so elsewhere, they could prepare such things in their home.
Alternatively, instead of a specific "sacred place", the creatures could just be vulnerable in something else's home. The creature itself might or might not be aware of this vulnerability.
The Returning ability could be tied to being broken into smaller creatures - they have the returning ability while they're small, but not when they're together. However being much less potent apart, the creature changes tactics because it needs to kill them.
This, of course, is entirely dependent on the creature(s)' motivations, which only the GM can determine for his campaign.
Assassins? Spies? Thieves? Something else? That heavily varies what they should be weak against, and you need to choose something that is appropriate for the story and, more importantly, something you think your PCs would not only have the ability to acquire but would want to do so in their own home.
How this relates to any of the above abilities is up to you.
Perhaps they can only "die" (and thus only be forced to return) under the above conditions. Another option is, of course, that they don't have the Returning ability at all, but have some sort of multiple use "split" ability to gain their multiple small bits, that has limited number of uses per day, or a "cool down" time to allow the PCs to force them into one larger creature.
In any event, this is the least defined suite of rules, because "why the PCs can't get rid of them" is entirely based on the game you're running. It's thus up to you as you like.
Next I'll take a look at the type of creature you're creating. Again, it might be a bit, as this stuff takes a while to read and think about. :)
What about someone with Swarm Skin cast on them? Break up the swarm into chunks, one per party member. You'd have to deal with the bones somehow, Animate Object from an allied caster maybe?
So, hey, everybody, I've got a big surprise: apparently, I have "life"! I know! I was shocked, too! Sorry for the large delay. :)
First... Swarm Skin + a Contingent Animate Object spell is actually a pretty nifty variant. I didn't even know Swarm Skin exists, so that's pretty sweet.
But I'm also dedicated to going over this thing so, in addition to that, let's look at more creature types and options.
Deciding what exactly the kind of creature you want to have doing this is pretty important over-all.
A few people have mentioned some rather exclusive monsters in a bestiary somewhere or in an older edition (all of which have a high CR). I'm not sure what those are, so I can't really comment on them.
That said, let's look at some of your options.
Are you interested in this creature being more:
- bestial?
- of a caster?
- monstrous, but not bestial?
- humanoid?
- assassin (hired or otherwise)?
- thief (hired or otherwise)?
- investigator (hired or otherwise)?
- instinctual?
- methodical?
- subtle?
- obvious?
- or something else I'm not thinking of right now?
Once you have the basic structure in mind, you can actually start looking at the kinds of creatures you can use. Note that not all of the above are exclusive to each other. A bestial creature could be instinctual and either subtle or obvious, while a caster could be equally variable. A thief could be a caster, an assassin, an investigator, or any combination thereof (similarly any combination of those at all works).
So, here's a few quick ideas you could flesh out more, if you like:
* Shadows or other incorporeal undead. These creatures make for excellent investigators and assassins, and can be subtle or obvious. Their incorporeal nature makes it easy to describe how they fuse, and the weakness to holy places makes sense for them. They tend toward the instinctual side (look at their intelligence score), but they aren't bestial in nature and can be used methodically. The basic idea: take four shadows, grant them the traits I note above, and unleash them on your PCs. When they fuse, they can become a greater shadow. You can do something similar with pretty much any incorporeal undead just as thematically easily.
* Doppelgangers, Rakshasas, or other similar shapeshifters. These creatures make for excellent investigators, assassins, thieves, and tend strongly toward the subtle and the methodical. They're both humanoid and monstrous, but the Rakshasa has a tendency to be almost bestial (though not feral) while the doppelganger is rather removed from it all. A Rakshasa makes an excellent caster and with a few extra levels could have the contengency, animate object, and swarm skin spells itself (at least if you fudge just a little and let it be on their class spell list). If you want to use both, you can say that the lesser versions use doppelganger stats, while the fused version uses Rakshasa stats. If you like the mechanics, but not the thematic elements, repaint it as something else. For example, perhaps they're a kind of sentient, shapeshifting ooze called "otto" or "dominion" instead, that just happen to have the same stats and abilities as the above creatures, but the ooze type, which would impact it's HD value, skill points, base attack value, and base save values. Heck, you could have it be an Outsider (native, ooze) which would only impact it's immunities by granting it ooze traits (though, since it's not mindless, it wouldn't have total immunity to mind-affecting effects).
* You could do something like ogres that fuse together into a troll. While this may, at first, seem counter intuitive, do remember that ogres were often thought of as having shapeshifting powers in old fables, which would fit this perfectly. Much like the doppelganger/rakshasa creature types, though, you may feel that you want to reskin them. In this case, it could be simply calling them "uthraki" (or something else of your design), describe it as a hairy, clawed ape-like creature with lots of eyes (or some other interesting description) and you're good to go. One interesting variant if you like the swarm skin effect is to have a caster hire the creature, and give it a potion of said effect, then animate the skeleton for it (either as an animated object, or as an undead skeleton - the ogre could reassemble itself around it's skeleton only to find it's now a zombie!), for some reason. These guys make great assassins and thieves (though very unlikely investigators or casters), are bestial, and tend toward the instinctual side instead of methodical. They are obvious and not subtle. If the ogre->troll change doesn't seem strong enough, you can add the advanced template to the troll to net a +1 to its CR (you can use this trick with anything, really).
So, anyway, there are just a few basic ideas. If you want a bigger creature out of it, you could always add the giant template either in addition to or instead of the advanced template, as another idea.
In any event, I'm out of time, so I hope that helps!
These are pretty helpful things to consider so far. Much more in depth analysis than I expected!
I haven't fleshed it out yet but the idea I'm considering now is some sort of chimera type monster.
Over the adventure the PCs have killed a number of familiar toting spell casters and I'm toying with the idea of them returning as some sort of incorporeal undead possessing the same animals they were associated with.
I'd turn the animals somewhat monstrous with some advancements but overall they'd be only be minor threats individually. (That goat has been following me for 3 hours...and why does it have 3 eyes?!)
However each time they slay one the undead simply disappears only to return later inhabiting another of the same animal.
On the final day I'm envisioning an attrition battle of sorts where the spirits are constantly jumping hosts the instant each one is slain so the PCs are under constant harassment forcing them all to retreat home.
At some point when I guess they run out of goats or whatever the BBEG or an agent of it shows up to mock the undead's failure and punishes them by somehow merging them and the animals into a hideous amalgam.
EDITED: multiple times really fast to fix some broken links. Sorry.
That's pretty cool, actually!
A few templates you might want to look at in that case:
* For multiple as one rules: Abomination and Amalgam, Collective Creature.
* For thematic "that animal isn't right" rules: Bipedal Creature, Fey animal, Ogrekin, Mana Waste Mutant, Manimal, Shadow creature, two headed. (also the simple templates of celestial, entropic, fiendish, and resolute).
You could even have each of the different mage-spirits or whatever come with a different unique template (one being fey, one being two headed, one being shadow, etc).
When they combine, you could also add things like the bipedal or manimal templates and maybe even the ogrekin or mana waste mutant (though I'd lean to ogrekin because of it's fun mechanics) after the amalgam template (which is really the one I'd suggest from the top list) with the advanced template layered on top.
As for the undead themselves, may I suggest a young, nocturnal ghost with the following caveats: use the quick rules instead of the rebuild rules on the young template (resulting in a +2 to DEX-based roles, but a -2 to all other rolls and -2 hp/HD compared to whatever the ghost would normally get), the light sensitivity may or may not apply at your option from nocturnal while they're in animal form, and the ghost only has the rejuvination and malevolence abilities but the malevolence only functions on animals.
This makes them persistent, but not really threatening in any way.
Anyway, I hope that helps, and it sounds like fun!
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