These are what give the Omniars their abilities and thought processes.
when the Shardians And Xharias where creating the Omniars they gave them the Ability to create these cores but in order to activate them, they would require the "life energy" of a living being. this would of been a safety measure to stop them to over replicate themselves. but it backfired when a small error in the code allowed them to have emotions which made them realize that the war that they were fighting was futile, pointless. so this made them leave and seal up the Shardius Ring.
omniar cores would of been given to a creature who deserved it, or with the case of the brain infusion fleet known as the flock, the Omniars felt the same pain, they like the Omniars were created for war, as a disposable object. so they gave each member a Core to use.