Six Arms has no other name (comprehensible to people who speak English anyway), and resembles a six-armed dark brown-grey snake that is somewhat anthropomorphic. Zie was of the 3rd gender of a 3-gendered species.
Zie was a medical scientist, working in a laboratory on a moderately tech-advanced world. Zie died when someone broke into the laboratory and stabbed Zim.
Six Arms was working on genetic test-tube babies of the snake-like race's 3rd sex, something like a catalyst gender required for procreation.
Star does not remember much more about Six Arms' life.