Diebethar
Located in the Galactic Core of the Milky Way and, ultimately, all other galaxies of the Virgo Supercluster.
Diebethar is estimated to have ruled over ten billion worlds, with a total population of over ten septillion living beings.
After its defeat by the Virgo Cultures, it took the Gergathan a million years to recover power and influence. Although hindered by the Free Peoples of the Scattered Worlds (and particularly by Jel Haran and Lirith), by 21 million BCE the Gergathan had regained enough power to start reconquering the Milky Way's Core, and to proclaim the third great Core Empire, Diebethar.
Through treachery, guile, and division, Diebethar rapidly spread through the Local Group and beyond, meeting and defeating the Virgo Cultures about 19 million BCE.
About 5.2 million BCE, the Avethellan Empire led an assault against Diebethar and Messilinia, and the Avethellan hero Kylvin struck at the Gergathan with one of the Singing Stones. However, Kylvin's Strike—like Forriva's—was blunted at the last moment.
Nonetheless, Diebethar fell, and the Core was briefly integrated into the Avethellan Empire. About 5.19 million BCE, Diebethar was succeeded by Malreppidar.