That works as well.
The Archivist cold be folded into the Avenger as the seeker of knowledge over the default Avenger's slaying seekers of forbidden knowledge or monster against the order's tenets.
Do you one better: They're the maintainers of the "black archive" type stuff, in addition to being the ones who hunt down the makers of such things. Know your enemy, that sort of thing.
That's what I did with the effective Avenger-equivalents in my Jewel of the Desert game. They're the internal police of the faith--they very rarely do anything to ordinary laymen, instead focusing their attention on planar threats and wayward clergy who abuse their powers. In-setting, they're called the
Asiad al-Khafyun, the "Secret Masters" or "Hidden Overseers." The predecessor organization itself went rogue a long, long time ago, so this one takes extra special care to ensure unwavering dedication, including magical brands on the flesh (in discreet but accessible places.)
When you aren't hunting down heresiarchs, you're keeping meticulous records of their doings, tactics, warped theology, etc. A dangerous job in a world of magic, but a necessary one when you can't rely on bolts from the blue to delete heresy the moment it shows up. For my Asiad al-Khafyun, their primary tasks have been to hunt down members of the predecessor organization that went rogue (the
Zil al-Ghurab, "Raven-Shadows") and to prevent the spread of an infectious, parasitic spirit, the Song of Thorns, from its (effective) prison in the perpendicular plane of Zerzura. (As usual, adapted from the very excellent
The Gardens of Ynn by Emmy Allen.) I've taken care to portray my version as
very scary but really, really dedicated--carefully selected and put through training from hell.
