One of their first destinations was Doien, the homeworld of the Leviathan Pilot species, the closest planet to the portal from "Grey Space" which opens every 25 cycles. Once on the surface the Grennij engaged in the brutal subjugation of the peaceful Pilot population.
The Grennij were merely serving as shock troops for the Kkore, a position which sees them battling and conquering several planets and kingdoms. The weaponry used by the Grennij was relatively primitive barrel loaded projectile rifles, though their ships carried authentic Kkore cannons.
This favored position was terminated by the Kkore when they discovered the Grennij sought and used the weapons technologies and supplies of conquered peoples, a step Ddan-Myr and the rest of the Kkore regarded as first on the path to Grennij betrayal.
The Kkore pre-emptive strike devastated the Grennij population, with a relative minority surviving the purge, the survivors, found by Scorpius, proved instrumental in the allied Armada which eventually succeeds in routing the Kkore and destroying the mega-carrier Agrona, killing the Kkore monarch Ddan-Myr.