Aberrant nature. The parasite does not need to sleep or breathe, and it has a lifespan of 2 days when outside of a host. Also if the parasite dies while within a host it dies as well.

Amorphous. The parasite can move through a space as narrow as 1 inch wide without squeezing.

Psionic burst. Each creature within 5 feet of the parasite must succeed on a DC 10 Intelligence saving throw. On a failed save, the creature takes 1 point of psychic damage

Parasitic infection. In order for the parasite to infect a creature's mind, it must crawl into the creature's skull to attach to its brain.

  The ritual for  infecting a new host has a casting time of 1 minute, and the parasite must be within 5 ft. of the creature it's attempting to infect; Components, S. (Crawling into the skull)

  The parasite must succeed on 5 opposed DC 12 Intelligence saving throws in order to infect its new host. If the parasite fails all 5 saves it is stuck outside of a body, and the creature that it had attempted to infect is now immune to becoming infected again.

  If the parasite infects a new host it falls unconscious for the next 1d4+1 hours, during that time the parasite adopts the host's stat block and gains its abilities. Except that the parasite still has this action, it gains resistance to psychic damage in this form, and it keeps its Intelligence, Wisdom, and Charisma scores.

  (The parasite can only infect creatures that are, Small or larger, Aberrations, Beasts, Fey, and Humanoids).