The Ancient-Wraith War was the century long conflict which lead to the destruction of the Ancients as a civilization. After travelling to the Pegasus galaxy in Atlantis, the Ancients, now known as the Atlanteans, seeded many planets in Pegasus with Humans, while colonizing others. One of these planets, however, was home to a species called the Iratus bug, a creature possessing considerable immunological capabilities. The bugs began to feed on the humans seeded there, and as time went on, they began to mutate, taking on many advantageous characteristics. This brought about the creation of a hybrid species known as the Wraith. Eventually, the Wraith, needing to feed on Humans, began a conquest of the Pegasus galaxy.