The Lellish are a xenophobic humanoid species. Physiologically, Lellish are humanoid with their only known external difference from Humans being a series of horizontal ridges down the back of their neck and along their spine. Lellish traditionally mate for life. When two Lellish have intimate relations, they experience olan'vora - "the shared heart". This makes their body chemistry interdependent, causing withdrawal symptoms if the two people separate. The effect gets stronger with each mating and separation can be fatal.