Unnoticed by the crew of the USS Brattain and later the USS Enterprise-D in 2367, the being tried to communicate with the crew during their sleep and was responsible for a long-lasting loss of REM sleep in the respective crews. Betazoids were able to communicate with this being in their REM phase, although the communication proved difficult for the Betazoids to interpret.
After the Brattain became trapped in the same phenomenon as the being, it tried to communicate with Andrus Hagan, the Betazoid science adviser on the Brattain, while he was asleep, and was thereby inadvertently responsible for the madness and eventual death of the Brattain's crew – all except Hagan, who was left in a coma-like state.
When the Enterprise-D became similarly trapped, Deanna Troi was able to communicate with the being and discovered that it was trapped in the Tyken's Rift as well. With Data's help, the Enterprise-D crew planned an attempt to leave the rift by helping the being to create an explosion. Doctor Beverly Crusher induced REM sleep in Troi, who informed the being that the Enterprise-D would assist its efforts by releasing hydrogen from the ship's Bussard collectors. The being finally appeared as a bright humanoid silhouette before Troi woke up.
"See the eyes...in the dark! One moon...circles!"
- -Tyken's Rift being describing hydrogen (2367)