
Deaths Adorable Apprentice |

In the game I am running there is a seal leaking necrotic energy and the players unintentionally let a bad guy know with a few months to plan when to attack it. So while the guard is lessened to guard a different location where other plot stuff is happening I want to have the baddies attack it.
So the seal is being guarded by a group of Fey and a bunch of clerics and paladins of Iomedea. This fight is going to happen off screen but the players intend to head that way, time-wise, after the fight happens.
Most of the baddies leading that attack are necromancy focused Wizards, Sorcerers, Witches, Rouges, Barbarians, and Clerics. My campaign has a strong necromancy bent.
I want to steal the soul of the Paladin, cause it sounds like fun. What can the bad guys do with the soul of a Paladin and maybe a few clerics or powerful Fey?
Any suggestions legal and mechanically sound or less legal but fun sounding are welcome and wanted.
Thank you in advance
DAA

The Sideromancer |
So the seal is being guarded by a group of Fey and a bunch of clerics and paladins of Iomedea.
I gotta say, that sounds like terrible team chemistry.
Since Fey reincarnate on their home plane, it might be interesting to set up a Fey soul so that it thinks it's on the First World, and continuously kill it for an infinite supply of corpses. You can then use the corpses for construction, heat, undead, and probably a few more things after a Polymorph Any Object.

Dastis |

There are 2 ways(most of the time) to take a soul in pathfinder; infernal contract and just ripping it from their dead body. Since its a paladin and you mentioned combat I'm going to cover ripping which is covered extremely well in Book of the Dammed III.
The easiest way to gain soul gems is through cacodaemon. Their special ability lets them trap the souls of the recently slain in soul gems. They are usually accessed via Summon Cacodaemon or Greater if there's lots of souls to claim. Planar binding/ally also works if they don't want to spend a slot every time. There is also a 3rd level spell that makes a single soul gem but it is higher level than summon cacodaemon, doesn't have any uses like a summon, only does a single soul, and has a material component. Soul gems are valued based around the purity of the soul, hd, and religion in life(those who worship good gods are more valuable). Interestingly this gives an actual reason to kill good people in particular. Prices typically range from 100gp for a typical human to 5000gp for a high level heroic individual.
Non Sparknote version
As for uses they are primarily used for item crafting. Soul gems count as materials for magic items equal to their market value. Of note here is that it is possible to deliberately craft intelligent items. It is left open ended as to whether the intelligence is that of the soul or another being fueled by the soul gem. In addition soul gems can be used as material components of market value. Several races of evil outsiders, mostly daemons, gain bonuses when they consume soul gems. There is also a market amoung outsiders for such soul gems. You can sell them on the black market, use them as an offering for planar binding/ally, or trade them for infernal contracts/favors
Lastly, the soul drinker PRC is based around having a pool of soul points gathered from their negative level touch attack. They can use it for several different things, most notably recovering spellslots.

Paladin Trap |

What about warping his soul and having him return as a powerful undead? He is unwillingly bound to undead and maybe even if he has to fight the good guys he still wants a way to be released.
Maybe he is bound to a phylactery-like object that the baddies have and he can only be destroyed permanently and his soul released by destroying the object.
That could be an interesting side quest for the PCs, to free the soul of the paladin. Here, playing him as an unwilling enemy even if he is forced to fight recklessly could be fun to do.

Deaths Adorable Apprentice |

It it horrible team chemistry that is only happen due to a common enemy but there has been pleanty of issues happening on that front between both groups that the party is only now going to be aware of. And the spamming corpse thing is rather evil :)
I had never considered a cacodaemon but I will look into them. And I will be looking into that prestige class. Thank you for that!
I do not think I want the trade option. I will save that for the Night Hags later.
I am defiantly wanting them to try and recover the soul or at least free it if they are able to. But it will take some time. A pwoer source for a powerful undead could be a fun option.
What kind of critter should I use for the Paladin? And if I were to get the soul of a Nymph what should I make that into?