Less of a weapon, really, and more of a tool.
Although it is nonmagical, you can wear this small iron ring with a vicious hook on the end to amplify necromantic spellcasting. Whenever you need to make a physical sacrifice to cast a spell, you can count as having sacrificed 5 more hit points or 1 more CON, DEX, or STR than you really did. You cannot reduce your sacrifice to zero using this ring. This item takes up a ring slot even though it is nonmagical.
Weight:-, Cost: 20 gp, No aura
Weird, yeah. Some will be reminded of a certain character from a Neil Gaiman book, although I think Despair’s ring functions a bit differently.
Great for the big bad evil guys to give them a unique flavor, or for a strange and suffering player character.