The original Ryloth, before Lucas stepped in and screwed up the planet, was disturbingly dark. West End Games, which named and designed the Twi'lek people for the first Star Wars Role Playing Game created a whole ecology around the Twi'Lek and it was them being underground dwellers, raiding and feeding on one another in pure darkness and that bestial nature of the Twi'lek that I loved.

Did you all know that the Twi'lek originally only came in green? Bib Fortuna was an albino and an outcast due to his mutation. The purple, blue and other colours were added later in various comic books. They also changed the entire structure of the planet at some point, turning it from a tidally locked world to a desert planet. This, was a bit frustrating since the West End Games guys put a lot of thought into the Twi'lek. They determined that the Twi'lek lack of hair, the ear cones and the lekku would indicate a subterranean evolution. A sensible supposition. In a sense, Twi'lek were like "naked mole rats". Being subterranean hair was not useful and never evolved but their lekku served as a delicate instrument in detecting the movement of other beings in the darkness.