An instrument mimic poses as a musical instrument, most often as an instrument of the bards. They seek out caches of treasure or music halls to hide among valuable objects or other instruments.  Once picked up by an adventurer, an instrument mimic will travel with its new owner.  By night, while the owner sleeps, the mimic will rummage through their belongings in search of food or sheet music to read and learn.  If discovered (usually when a new owner attempts to identify it) an instrument mimic will often try to negotiate; offering to serve the adventurer with its bardic power in exchange for regular payments of food.

These mimics imitate musical instruments not only in appearance, but also in function, and can produce beautiful music.  They are an intelligent variety of mimic with a great appreciation for music.  Like the magical instruments they imitate, they are very particular about who they will allow to play them, attacking a player they do not approve of with vicious mockery.  Also like the magic instruments they pose as, they grant a wielder they have bonded with the use of their own spells.

Variant: Mimic Instrument

Some instrument mimics are willing to serve as instruments for bards. A mimic acting as a bard's instrument gains the following trait:

Mimic Instrument. The mimic can be wielded as an instrument, and functions as an instrument of the bards.  While acting as an instrument of the bards for another creature the mimic takes no actions of its own.  An attuned wielder can command the mimic to polymorph into a different instrument as an action.  While holding the mimic, an attuned wielder shares the mimic's Innate Spellcasting trait, using its own spellcasting ability and spell save DC in place of the mimic's.  Additionally, an attuned wielder can command the mimic to cast a spell from the mimic's Spellcasting trait, requiring the spell’s normal casting time, using the mimic's spellcasting DC, and using the mimic's spell slots.

While polymorphed into an instrument, the mimic also functions as a mace.  When a melee attack using the mimic as a weapon hits while the mimic is polymorphed into an instrument, the target is subjected to the mimic's Adhesive trait.  While a creature is subject to the mimic's Adhesive trait, it cannot be used to make another weapon attack, can't have spells cast from it, and can't be used as a spellcasting focus.  Ability checks made to disarm the mimic's wielder by removing the mimic from their grasp have disadvantage. While being held by an attuned wielder, the mimic shares its Grappler trait with its wielder against any creature subjected to its Adhesive trait.

The mimic is immune to game effects that would damage or destroy weapons with acid such as a black pudding's Corrosive Form trait.  Non-acid game effects that would damage or destroy weapons deal 1d6 damage to the mimic instead of lower its damage rolls.  If an attack or game effect would reduce the mimic to 0 hit points while it is being wielded and its wielder has at least 1 hit point, the mimic drops to 1 hit point instead.  While the mimic has 5 hit points or less, it cannot be used to make weapon attacks, and the wielder loses all benefits provided by the mimic.  The mimic is considered a destroyed weapon until its hit points rise above 5.