So I've been looking over the spell Planar Ally since I think it's a fascinating spell for the purposes of not only Roleplay but also enhancing combat capabilities as well, but speaking as someone who is playing an Urgathoan Necromancer for a Vengeance campaign, I've hit a bit of a roadblock in what would directly benefit me and my playstyle. If I were to summon anything I'd want it to be something that would benefit my character's abilities as well as his undead.
With this in mind, I must also point out that apparently extraplanar undead like Shadows already fill the ranks of what you can officially summon with the spell, but unfortunately the listings of what undead do and don't count as Extraplanar isn't listed in any undead's statblocks as far as I'm aware.
If anyone has any ideas for what Outsiders I could potentially summon with this spell that would benefit a Necromancer, or even just any Undead that would count as Extraplanar enough to be summonable, that would be a great service, thanks.
Fiendish creatures are described as being able to be summoned by spells like summon monster or planar ally, so I'd think planar binding as well. You can therefore call and bind fiendish undead that inhabit Urgathoa's domain in Abaddon or, the Abyssal Realms of some Demon Lords. Personally, I wouldn't make any problems with calling untemplated undead as well, as long as they originate from another plane, for example from the Void (Negative Energy Plane).
Inner Sea Gods also list several Urgathoa's divine servants, who are also clearly written as answering planar ally spell and similar spells from the faithful. They include: Barasthangas (unique devourer), Fjarn (unique ghast), Olix (unique fiendish vampire) and Mother’s Maw (Urgathoa's herald). The same book also describes sarcovalt an outsider aligned with Urgathoa that looks like a mix of a giant fly and an undead vulture.
Finally, you can also call daemons. In The Great Beoyond: A Guide to the Multiverse it is written that they have some sort of deal with Urgathoa and Zyphus, they don't attack their domains or the souls and clergy traveling to their domains. They don't serve them in any way, but followers of those two gods may have an easier time dealing with daemons than other mortals. You can call cacodaemons to create soul gems that you later use in necromancy, but other daemons could also work, even if they are associated with death rather than undeath.
If only there were some way to search for any and all undead that inhabit that domain, but my searching ability must be weak because I couldn't seem to find any. I did, however, find the Dust Ghoul, which is an undead that spawns and originates from the Earth plane as far as I can tell, so I know there must be more.
Are there any specificities to the unique divine servants Urgathoa has (AKA are they statted?), or are they merely mentioned and nothing more? The Sarcovalt is also interesting and I've taken note of it, but I'd rather keep poking around for options since they don't seem to actually DO all that much, at least when it comes to actual undead-related activities.
As for Daemons, Soul Gems are a very interesting concept that I might just have to take advantage of sometime in the future, especially since my Necromancer has a... unique take on how souls work. I wonder what the ramifications would be of placing a Soul Gem inside the raised body of the person that body used to belong to. (Obviously by RAW it would do nothing, but I'm sure that's just because it's a question the devs just haven't considered.)
d20pfsrd Advanced Monster Search lets you find undead with extraplanar subtype. Most notably, it includes bodak, devourer and several types of nightshades, these creatures appeared already in Bestiary or Bestiary 2. Additionally, I believe that any undead that is created on another plane, for example from mortals who dies in the Negative Energy Plane, no mather what kind, should get an extraplanar subtype.
Out of the named Urgathoa's servants the statted ones are only her herald Mother's Maw (CR 15, 18 HD), and a generic sarcovalt (CR 4, 4 HD). The others have only descriptions that say in what way they are unique, but can be built by modyfing generic creatures of their kind.
Book of the Damned, Vol. 3 - Horsemen of Apocalypse mentions several uses for the soul gems. They can be used as a source of magic power, replacing costly spell components or components for the construction of magic items. They can be used to create intelligent magic items. The GM can invent new uses for them, whether creating new kinds of undead, empowering existing ones, or creating unique spells or rituals.
As a note, shadows--most of the time--aren't extraplanar any more than a skeleton is--they don't have the extraplanar subtype. They're only extraplanar if they're not on their home plane. By definition, any creature you call with planar ally is extraplanar, whether it's a shadow, a skeleton, a celestial weasel, or a titan.
A shadow called via planar ally is a good candidate for a simple template, such as fiendish:
Creatures with the fiendish template live in the Lower Planes, such as the Abyss and Hell, but can be summoned using spells such as summon monster and planar ally. A fiendish creature's CR increases by +1 only if the base creature has 5 or more HD. A fiendish creature's quick and rebuild rules are the same.
The good news is that unless you know the name of a particular individual you're trying to call (and technically even then), it doesn't matter--the deity is the one who decides what answers your spell, not you. So Urgathoa could just as easily send you a giant carrionstorm or some sort of daemon rather than a fiendish shadow. That's up to her whim. If you're casting planar binding, your options are far greater, as you aren't limited to servants of your deity.
Well unfortunately clerics don't really have access to Planar Binding without making use of a UMD check, and I'm already spreading my funds thin enough that I'd rather not have to start resorting to using mid-level scrolls from other classes.
I'm also asking this on a pre-emptive basis for my GM, like I said I'm going to have to wait a little bit before I can actually get down to calling Allies to assist with my efforts, so until I can actually get that train rolling I'm looking to give him some kind of list of creatures that Urgathoa might actually _want_ to give me depending on the task I'm setting out to do. After all, if this were something like Asmodeus or something like that knowing what kind of Ally I'd likely get would be a piece of cake, but unfortunately Urgathoa just doesn't have many built-in Outsiders to work with without resorting to the kind of in-depth research or jumping onto trains of logic like we're doing here.
All of this said, once I gain access to the level 6 version, do you guys believe a Daughter of Urgathoa would be an appropriate response to the calling of the spell? If so, do you think it should be one of the named ones or should we take one from another plane so she's still technically an Outsider and just apply a template to show as such?
Lore-wise, I don't hink that Daughters of Urgathoa would fit. They are created when a favored female priest of Urgathoa dies while Urgathoa prefers her to stay longer on the Material Plane. I imagine they retain their class levels, so you'd never find a generic Daughter of Urgathoa without several cleric levels.
I have another idea though: instead of making undead outsiders, let's make outsiders undead. Urgathoa can have many undead outsiders under her control, for example cerberi ghouls, zombie formians, vampiric genies, or graveknight devils. When you look at it like that, she may have the widest selection out of all the dieties.
I imaine she may be willing to answer planar ally by sending liches. Not only they can be specialized to deal with a wide range of problems, even if they fail and die, they are going to regenrate from the phylactery the've left under Urgathoa's care.
I'm liking your idea for already undead Outsiders, I've made a few of my own from some of the Angels and Devils we've fought during the course of our Vengeance campaign, so the thought of others that have already been created being sent my way seems like a good fit. Probably going to avoid any liches though for the same reasons you point out a Daughter wouldn't fit, while there IS a generic templated creature in a statblock my character I feel would be of a lower rank than a lich and they also retain class levels when gaining the template.