If that's the case, then I'd see this more as an ET creature than a playable one. If they 'basically' ask for a protagonist to kill them, what's the point of playing it? It's not your job, as a player, to create a creature that asks to purged by adding certain things that a large group of players can detect.
Good lore, still. But I would moreso acknowledge this as an ET creature, rather than being playable.