Key Features for an Anti-Supernatural Class

[Sagetim]

I want a Prestige Class which fills the role of Occult Slayer or Witch Slayer, but one that works better as a PC class, so: (a) it's effective against general threats in addition to the specific Mage / Binder / Witch / Occult threats, and (b) has feature strong enough to justify inclusion in a party.

I also want to tie in feats like Mage Slayer from Complete Arcane.

Where else can I look to steal ideas for class features & mechanics which are congruent with those classes, and that feat?

Thanks!

depends, if we're talking pathfinder, then Mystic from Dreamscarred Press (an initiator class) has a lot of capability in resisting spells (going so far as to have a class ability that lets them will save against ref and fort spells that allow a save for partial effect, being a wis based class with a high will save, and having a scaling bonus against spells, spell likes, psionics and psi likes). And, you know, then you have maneuvers that you can spike damage out with.

With regards to 3.5, Sword Sage will get you where you're going. You might need to mix in something else to get your attack bonus up, but Shadow Hand Maneuvers and striking from stealth to outright murder the caster while they're incapable of actually detecting you is going to be the bread and butter that you use to shut them down. As long as you stick to strikes that aren't supernatural in their nature (like mountain hammer, for example) extra defenses a spellcaster can deploy against spells won't help them any (ignore spell resistance). Some of the more tricky to deploy maneuvers against monsters (the ones that force a fort save) are going to work a lot better against humanoids, because they tend not to have vastly inflated constitution scores.

One of the main things in going for maneuver users is that instead of dispelling your target (which pathfinder does have a few maneuvers for in Elemental Flux) you're going to go for using strikes that let you ignore damage reduction if they have stone skin up, strikes that hit areas if they have mirror images up (in desert wind and elemental flux, depending on edition), and just generally beating the target to death. There's maneuvers for staggering, stunning, dealing ability score damage, throwing, and even just doing large amounts of raw damage to single targets (maneuvers are generally much more limited in their aoe capacity). Outside of strikes, there are stances and maneuvers that vastly increase your mobility beyond 'I move 30 feet, maybe 60 on a charge'. Teleporting effects, spider climb, and flight, things that spellcasters are used to being the sole benefactors of, are things that you can do with a maneuver user and level the playing field from their supposedly unassailable position. Hell, in pathfinder there's a boost at mid level that lets you be ethereal for a full round.

edit: Also, use iron heart surge responsibly. Remember that it takes a standard action and you have to be able to move to use it. That said, it ends the source of effects. And any reasonable DM will at least tell you that no, you can't turn the sun off with it just because of poorly worded and unerrata'd phrasing. At most they might slap you, I dunno.