The current genre and vibe of the opening is a relatively cute mystery focusing on relatively light drama in the opening years of the fragile peace; Stairside is on the bottom side of the Great Staircase near to the living room, and scenario going on is that there is a hubbub going on about the Sluagh embassy and the Grand Imperial Army stomping about under Lieutenant D'arcy in search of some kind of thief.

With this context, whomever you feel of your people fits that vibe will be appropriate. If you go with Tenebris, then this is likely a stepping-stone adventure on their path towards their actual goal elsewhere in the house for the time being.