So the Vaulters came to Auriga when they crash landed? If so how do other human factions live on Auriga? Also where did the Vaulters come from? As I though that the Endless took over the universe. Or did the Endless create the humans like they did Auriga's other species? If so how did the Vaulters crash land there in the first place? In short, what is going with humans, The Endless and other species on Auriga and even in the universe? Did they Endless create them all in experimentation?

From my understanding the vaulters are only a portion of the Mezari that landed on Auriga. The rest of them came to the planet together but managed to make it to the surface and survive out there, this developing their distinct cultures.

It's sorta explained in Dungeon of the Endless. Basically, most of the races all descended from the people who were on the space ship(s) that crashed to Auriga.