Skelemallet

Weapon (mace, skeletoy), very rare (requires attunement)

Skeletoys are objects that Underhell fiends use as their monstrous tools. Most of them are made up primarily of spinal columns and skulls, but other configurations also occur. Generally, mortals can’t use one of these items effectively unless they trick the skeletoy into believing they are fiends or acting under the direct orders of fiends; in such a case, the item will not oppose them until it realizes the truth. All skeletoys obey any fiend who commands them, or a minion acting on that fiend’s behalf. In case of conflicting commands, the skeletoy obeys the highest-ranking individual to give a command. All skeletoys have the same special purpose: to further the fiendish invasion and protect all Archlords.

This mace is made of a short spinal column with a humanoid skull at one end. You deal an additional 2d6 thunder damage on a hit with this magic weapon, and you score a critical hit when you roll 18–20 on your attack roll with it. In addition, the skelemallet grants you advantage on any Charisma check made to play a drum with it.

Sentience. The skelemallet is a sentient neutral evil weapon with an Intelligence of 10, a Wisdom of 10, and a Charisma of 15. It has hearing and darkvision 90 ft. It has proficiency in the Deception and Performance skills and its skill modifiers are Deception +7 and Performance +7.

The skelemallet can speak, read, and understand Abyssal and Infernal. It sings taunting songs in one of those languages when it can see non-fiends and isn’t being used to play a drum.

Curse. When you attune to the skelemallet, unless you are a fiend you become cursed until the curse is removed with remove curse or similar magic. All attempts to be rid of the skelemallet or break your attunement fail while you are cursed. While cursed, you have disadvantage on attack rolls to hit fiends and you are unable to wield any melee weapon other than skelemallets.

Personality. A skelemallet is an eager helper in bloodshed, but also knows how to play to an audience. If the skelemallet opposes you, it pretends to be afraid of you and grudgingly willing to serve you in exchange for a promise not to banish it to the Underhell. It maintains the ruse just until its curse is laid, then gloats and mocks you.