Aeorian Earworm

A wiggling worm-like creature in a glass tube filled with liquid. Aeorian runes are inscribed of a metal lid.

To attune to this symbiont, you must hold it against the skin behind your ear for the entire attunement period, whereupon it burrows into your head and bonds to your skull.

Spells. The earworm has 4 charges. You can cast the following spells from it, expending the necessary number of charges (spell save DC 15): detect thoughts (2 charges) or Comprehend Languages (1 charge). 

The earworm regains 1d4 expended charges daily at dawn.

Symbiotic Nature. The earworm can’t be removed from you while you’re attuned to it, and you can’t voluntarily end your attunement to it.