The Invulnerable Coat of Arn
This is a set of armor that will fit any size creature. Once donned, the AC of the wearer becomes -10 and the wearer becomes immune to fire, electricity, cold, and fear. The bearer of the Coat also gains the power of poison touch (ST vs. Death) and Fear. (All creatures below 4 HD flee in terror -- no ST; creatures of 4 - 6 HD get a save versus Magic; creature of 7+ HD get a save versus Magic at +2.) However, such invulnerability comes at a terrible price -- once removed, the Coat drains the wearer of a level. If the wearer decides to try to avoid the level drain, the Coat will take its due at the end of 24 hours and every 24 hours thereafter.