Deilas Cyl was a male Trill who was joined with the Cyl symbiont in the 22nd century.

Deilas Cyl was a botanist, described as a pleasant, soft-spoken man of thoughtfulness and wit. Cyl once gave a presentation on light alternatives at a botanical conference on Halii, where he met Tobin Dax. (DS9 - The Lives of Dax short story: "Sins of the Mother")