Forerunners

The Forerunners are a alien species from the fictional franchise Halo. Their species was created on planet Ghilbalb by an hyper-advanced species known as the Precursors which were mythologized by them. The Forerunners weren't chosen for the Mantle by the Precursors and they went to war against each other. The Forerunner civilization won and drove them out of the galaxy. Eons of peace broke in until a parasite named The Flood invaded galaxy and threaded all life in the galaxy. The Forerunners fought a forlorn war against them. They activated vast superweapons named Halos to destroy all life in the galaxy. Before they done this they collected two pairs of every race in the galaxy and took them with them to leave the galaxy until the parasite was killed. After the Floods ostensibly defeat they seeded life again and sworn never to return to the galaxy.

Though their empire, the Ecumene, controlled a relatively tiny portion of the galaxy, they had influence through it. They classify either as a 2.7 or a type 3 civilization on the Kardashev scale.