Ah, alrighty then.
What if the upkeep was such it'd be very hard/impossible to live in?
As in, exponential upkeep. 1 scalp, 1 day. 2 days, 2 scalps. 3 days, 4 scalp. etc;
Resets every week or something. To stop a person from just destroying and rebuilding it, the exponential part could be tied to the claim instead of the altar.
Then it'd be impossible to use so a witch could live in the light, but it'd allow a group of witches to create a temporary safe-haven.
Uses:
1. If a daring group of witches wanted, they could create a temporary safe claim near Providence to trade at and prey on unsuspecting pilgrims.
2. A witch, or group of witches, intending to raid a town/claim could create a claim of their own to camp out safely to wait at until their fellows arrive or for tactical purposes during the raid. (such as storing loot or goading a scent)
3. I could foresee an interesting dynamic if a town decided to claim an area on the edge where the light meets the darkness for witches and pilgrims to co-exist.
Additional suggestion for balance: bile drain for witches should occur even when logged out in the light. Probably same for pilgrims. (tested it briefly, doesn't appear to occur while logged out atm)
Otherwise its totally possible for a witch with high enough biles to live in the light right now. Annoying, but possible.
The purpose of this structure would be to allow witches an immoveable, albeit temporary safe-haven.