Hi,
I'm curious if anyone can direct me towards any lore on this class? Whilst the Morrowind description claims they hunt 'evil' mages using 'evil' magic themselves, are there any organisations, famous witch hunters, or codified rules for such characters?

Where are they most common? I imagine Morrowind chiefly (the skills chosen scream Dunmer, and the diktats of the Temple specify the necessity of wiping out Vampires, people who do the wrong kind of necromancy and people who worship the wrong Daedra) - but is there knowledge of orders or factions in Hammerfell or even High Rock?

Are these people sanctioned by the Empire or the Mages Guild (Pre- and post- Traven), or are they rebels who break the law to destroy 'evil' magic?

I actually don't know much about this, in oblivion there isn't any information regarding this I believe, but I'm still curious about what other people might know about it

Good topic, in my opinion

I don't know of any lore backing this, but I think that, for the most part, they're basically bounty hunters who specialize in hunting down mages, or freelancers with personal vendettas against "evil" mages. But, of course, what defines "evil" is debatable, so those people would probably be working outside of the law.

Yes, these are specialized mercenaries who kill targets the Temple won't. By "Temple," I mean the muscular, dominating religion of a place. So, it could be the Tribunal Temple, or it may be the Temple of the Nine Divines and Sixteen Acceptable Blasphemes. Arkay's Vestry were infamous Witch Hunters, adepts, born under the Ritual, and taken from the Battlemage aristocracy of Nibenay. There were a few Reachmen in the sect, as well.

Not to be confused with Crusaders, who are psychotics and booty haulers.

In lore not so much, but I presumed they were bands of mercenries or adventurers paid by temples, a bit like those outside of daedric ruins in morrowind.
Not generally seeking out evil but anything that brought disorder to established group, and focused on one group as in mages / necromancers / daedra / vampires / cults / monsters.
Depending on where they were established and who funded there cause.

Aren't there a bunch of Witches in Skyrim? If there are I'd expect some sort of organization of Witch Hunters because they may become a nuisance. I don't know though they may be just a bunch of lone wolf mercenaries.

I would imagine different Witch Hunters would specialize in different forms of "evil", as well. For instance there would be Vampire Hunters, Werewolf Hunters, Undead Hunters, etc. All of these people would be capable of hunting other types of evil as well, but they'd specialize and carry different equipment depending on their preference. A Vampire Hunter may prefer fire enchanted arrows and cure disease potions - a Werewolf Hunter silver weapons and bait for the monster, etc.

Witch hunters are professionals hired to root out some forms of heresy, any malevolent magical practice and creature (monsters) which are result of such practices.
I strongly believe they are specialists within guilds or religious organizations.

I think Buoyant Armigers filled that role as well.