As is the often the case in Blades, there’s ample “blank space” to fill in for the Spirit Wardens. We know they’re anonymous, and recruited from outside Doskvol. They have considerable occult and sparkcraft resources, and are integral to keeping the city’s ghosts at-bay (that is, if you believe the Imperial propaganda).
In my games, the Wardens are effectively ghost-busting MI6 agents, right down to their numbered designations (Warden #99, Warden #98, all the way up to Warden the First). A single Warden can match supernatural threats toe-to-toe, and is capable of fending off several mundane opponents at once if the situation calls for it.
What are your Spirit Wardens like? Beleaguered ghost cops walking a strange beat? Hulls gifted with an unusual level of self-determination? Scientist-poets who treat the “public service” angle of the job as an unwelcome, yet necessary, evil?