Illensans are one of the few chlorine-breathing races of the Federation, a small group who consider themselves an underprivileged minority to whom nobody listens. Certainly Illensans are considered ugly by the oxygen-breathing majority, even though they are vain about their own appearance.
Illensan are pale green, with a spiny, scaly, and membranous covering resembling haphazard, oily, unhealthy vegetation. They have shapeless green hands, and two legs like stubby columns of yellow-green, oozing seaweed. Head-fronds hide their eyes; there are also too many dark, wet swellings to tell which are the eyes. When speaking they make a sibilant, hissing, moaning sound, and their waddling gait makes a soft slithering noise.
The race is most commonly seen wearing a loose protective envelope to keep out the oxygen; within, their atmosphere appears as a yellow fog. Combined with their body covering, this makes it very difficult for oxygen-breathers to see how they move.
Illensans tend to be good at managing small groups, and are frequently found in charge of wards at Sector General. They have refined palettes, enjoying meals such as gree beetles in yursil jelly with fryelli sauce.