The Fraal are an ancient "elder" race of sapients who once journeyed across the galaxy, "terraforming" (for lack of a proper term) other worlds. They utilized objects known as Keystones to activate their terraforming machines. Many Human colonists discovered Fraal artifact data on numerous worlds, and began to activate their ancient machines, although it took 30 crew members to do so, for undisclosed reasons.
While the fate of the Fraal is unknown, a clue may lie in the hives of aliens that swarm the planets they were known to have set terraforming tools in orbit above. As none are known to still exist, they are widely considered extinct; the fact that their terraforming machines were left unused supports this theory.