by a_traveler
The rules for Possession state:When a player places a cube on the Event card, he must liberate a citizen of his choice, who returns to the respective player’s supply.
I parse that as "the supply of the respective player". Unfortunately, each player has not just one, but two supplies: the "general supply" and the "personal supply" (as can be seen in the general rules for using Influence: "2 points: add a citizen from the general supply to your personal supply.")
So... A citizen gets possessed by the devil, and then liberated: is this citizen now available for use, or would you need to recruit them anew?
I also looked at the French rules, but they don't make it any clearer either, stating "qui retourne dans la réserve de son propriétaire", with there again being a "réserve générale" and a "réserve personelle".
(FWIW, lacking an answer, we ruled for now that the citizen was immediately available for use, since there's no other mechanic where citizens go back to the general supply that we're aware of - but really, who can tell: When demonic possession is involved, all bets are off!)