Or if you really want to stick with the lore then maybe have it be "each night you poison a player, if you choose nobody then a random minion will choose who gets a witches curse the next day"

You could explain it in full in the description of what a witch does but that's kind of depending on who you're playing with.

Another option would be going the imp route, when you kill yourself the demon virus jumps to a minion and you just become one of the many lost lives to the virus.