When one of your cultists completes a ritual, or when a district or ley line is completed players take their cultists back from that feature after gaining power or embuing ritual stones as the rules dictate. The cultists are not immediately available to be re-used, they must recover first.
Returning cultists are placed in the cult's chapter house "Asylum" area. The following turn they can be moved to the recovery room and then on the turn following that, they can be moved back to the ready pool and be used.
I like games where, even at a high strategy level, you get some sense of empathy with your forces. I used to be terrible at computer real time strategy games because I never wanted my little troops to die - particularly once the fashion turned to having veteran troops and heroes that could develop on their own! In Caverna I lose, a lot, but my clan survives with full bellies and lovely fields. In Happy Pigs, my pigs are always vaccinated before the season change.
It doesn't take much to add a small mechanic to help players anthropomorphise their playing pieces, but for me it adds a great deal to the playing experience - but how do you do that in a game where you're a bad guy trying to end the world and are rewarded for casting your dudes into cold waters to (hopefully!) be devoured by Terrible Things?
What Carcosa's madness recovery does is hint at *experience*. What did your cultists see when that district became whole? When they felt the... what? Cobble? Cold Obsidian? Something much worse - warm and pulsing? beneath their feet? Did they see the King himself when they completed the ritual? What are they doing while they lie in the asylum? Can the others, still in the recovery room, hear them moaning, whispering and laughing beyond the door? Do *they* remember *why* they were crying out?
You can engage with this sort of flight of fancy quite strongly (I definitely do!), or you can ignore it and march on with the game - it's up to you - but I think it adds some important, thematic texture to the game.
Sweet dreams, cult leader!