Well, "Advent" has a lot of meaning to Catholics. However, the Advent use ships like they came out from paper bags purchased from the Adult Toy Store. So, that being equal to other things in the game, I would suggest that there's enough of a disconnect between the art direction in the game and the "lore" created by the manual writers that anything goes in answer to your questions. Just as long as it isn't Space Elves, I don't much care.
The TEC are an offshoot of frustrated, talentless Elvis impersonators that discovered that rhinestones can power a warp drive.
The Vasari are an offshoot of opera villains and Paul Lynde fanciers who smoked too much, but their devotion to their stinking week brought them to find phaaaase space.
The Advent are naughty Catholic schoolgirls who... who will... I mean, they will just do what you... dang it, I pushed my own button right there. I'm off to hunt for pron, now.
