LILLITH OF VELOR is a series written by Douglas W. MacBeth, whose screen name was S.T. Mac. It was unfinished at the time of his death in a plane crash in 2001, nut the completed portions are preserved on his website, Infinity Bridge, which also includes his own raunchy Conversational Velorian and sundry stories by guest writers -- like his own, none are part of the current Aurora Universe Main Sequeence.
Lillith, whose full Velorian name is Lill'th Zenerha-Shar'a Velor, is a young Velorian Protector, assigned to the alien planet Tetra. There she must remain for the rest of her life, protecting the inhabitants, the Tetrites, from the Arion menace. The Tetrites are spider-like creatures, the sort that might have been fodder for a creature feature movie back in the 1950s, yet they are utterly charming. Especially Phil, short for Philanthropithitatus, a master interpreter of hundreds of languages and dialects, whose signature line is: "Invalid Information is Never Welcome."
In THAT WHICH ONE BEGINS, first novel in the series, Terran military pilot William Wesson is marooned on Tetra after accidentally flying through a wormhole. He and Lillith fall in love, of course, but their love can never be consummated until she figures out how to enhance him. When the Arions launch a genoicidal attack on Tetra, he and Lillith and the Tetrites fight side by side to defend the world they all love.