Humanoid aliens with two lekku ("brain tails") emerging from the back of their head. Consequently they have no hair, and some say no hair anywhere - as Ryloth is something of a hot world. They come in a variety of colours including pasty white and several shades of green, blue and red (dying out). Twi'leks have a strong but little-known warrior culture.
Aalya Secura is a Twi'lek Jedi, the only Star Wars character to appear in the Expanded Universe before the movies.