The Skull Censer was crafted in mockery of the sacred incense censers used by goodly faiths throughout the world. Built by the hands of devil worshipers, and consecrated with the blood of an unbaptized child, it was used during Black Sabbaths to “bless” the faithful.
The chains used for handling the censer are affixed to a human skull–rumors disagree on who precisely the skull belonged to, but it was undoubtedly a man consecrated to the priesthood of a lawful god. Long gold bands mounted within the upper jaw support the incense dish. Oddly, regardless of the incense placed in it, the smoke which rises from it is always brilliantly green, luminescent, and smells of delicious cooking meats.
Though pleasant, this smoke has a predictably nefarious purpose. Those subjected to it for prolonged periods will slowly be drained of their vital essence. It will leave them frail, and they are more likely to succumb to disease or minor injury. Whilst the user of the device grows ever stronger, feeding on their essences before abandoning their congregation to find a new one.
In game terms, anyone who breathes the smoke from this censer for 20 minutes or more will lose 1 permanent hit point, which is transferred permanently to the on wielding the censer. This effect stacks, but cannot affect the same victim more than once per two week period. So an evil priest could use this in a ceremony with 5 other people, and at the end of that ceremony each of those 5 would have 1 fewer hit points, whilst the priest would have 5 more hit points than she had before.
The victims of this censer are entitled to a save v. magic after each encounter, with a bonus to their roll equal to the total number of hit points they’ve lost. If they succeed, they notice that they have grown steadily weaker ever since they’ve been around this censer. (Though it will not grant them specific knowledge of the cause. If they started eating more grains around the same time they started being afflicted, they could easily attribute their weakness to the change in diet).