Kelvan Empire

The Kelvan Empire is a major power in the Andromeda Galaxy. It includes the Kelvan homeworld, Kelva, and many conquered territories. The Empire felt it was neccesary to conquer "inferior" species rather than to colonize planets.

Kelvan scientists predicted that within 10,000 years the Andromeda galaxy would be uninhabitable for their species, due to rising radiation levels. Around the 20th century the Empire dispatched multi-generational ships to neighboring galaxies, to find new territory to conquer and save their empire. The USS Enterprise (NCC-1701) encountered an expedition sent to the Milky Way Galaxy in 2268. In this encounter the Empire's representatives didn't regard the Federation as a significant block to conquest. 

Also in 2268, Commander Rojan (the highest representative of the Empire in the Milky Way) signed a treaty with the Federation President, wich he sent back to the empie 300 years later after meeting their representative, Tamar. (SS TOS (Gone Native))