Joined Trill are symbiotic lifeforms and are native to their home world Trill. Trill are a playable race in Star Trek Online and belong to the Federation and Klingon Empire. Joined Trill which carry a symbiont and were available as a bonus pre-order for digital download editions of the game.
 Physical features
The Trill 'host' is very similar to a Human except for their spots, which are mostly seen on the sides of their heads. These spots run from their heads down their shoulders and carry on down their torso and legs to the feet.
 Other information
The Trill race consists of both hosts and symbionts. The Trill symbiont is a creature which is implanted into a Trill host, and subsequently joins with it. Not all Trill become joined, and only a portion of their population is selected to be eligible for joining. It is known that over half the Trill population can be joined with a symbiont although this information is kept secret and instead the Trill are told that only 1 in every 1000 Trill hosts are capable of joining.
Trill host and symbiont once joined cannot be separated until the host is near death or has just died. Doing so would kill the host and possibly the symbiont if it is not transplanted into another host or returned to its natural liquid-based environment.
- Traits have been changed in Legacy of Romulus. The following section may contain inaccuracies.
Joined Trills are allowed four traits, two of which are pre-chosen.