The Four Great Empires
The Four Great Empires are the only civilizations to consolidate control over more than half of the Locus, as it was known at their time. Since the frontiers of the Locus are constantly expanding, the criteria for a Great Empire is easier to attain earlier in its history than later.
The empires themselves, in chronological order, are as follows:
Irsidu (~5500-4500 bp): the oldest of the great empires, they were strongest in life magic.
Gomla (~3500-2500 bp): the second oldest of the great empires, they were strongest in matter and mind magic.
Asryn (~2200-1400 bp): the most successful of the great empires, they were strong in all schools of magic.
Srothi (~1000-800 bp): The fastest-rising of the great empires, the Srothi were strongest in energy magic.