Elixir of Corruption

This elixir looks, smells, and tastes like a potion of heroism; however, it is actually a poisonous elixir masked by illusion magic. An identify spell reveals its true nature. If you drink it, you must succeed on a DC 15 Constitution saving throw or be corrupted by the diabolical power within the elixir for 1 week. While corrupted, you lose immunity to diseases, poison damage, and the poisoned condition. If you aren't normally immune to poison damage, you instead have vulnerability to poison damage while corrupted. The corruption can be removed with greater restoration or similar magic.