Trill Symbiont

The Symbiont is a sentient vermiform lifeform from the planet Trill. It is transferred from one humanoid Trill host to another upon the death of the host. The Symbiont takes with it all memories of the previous Trill hosts. Upon joining, the new Trill host will gain these memories. The Symbionts live in Caves of Mak'ala on Trill and are cared for by the Trill Guardians. They communicate with each other via electrical impulses transmitted through the milky water they live in.

The Symbiosis Commission oversees the joining of Trill and Symbionts. The general belief is that one in every 1,000 Trill are suitable for joining; however, the number is nearer to 50% of the population. This is a closely guarded secret because every year about 5,000 Trill become initiates while about 300 symbionts become available per year.