The great Krork Empire sleeps. They wait for the day of emergence, when they will be needed to fight off the greatest evil in the universe. They have slept for countless generations and now, they are waking to wreck revenge on those who destroyed their creators, the old ones. They awake to battle the Necrontyr.
Millions of years ago, in the final great battle against the Necrons, the Krork fought on the front lines. They were often seen battling off Necron assault parties. They were especially effective because of their fearlessness, having never been infected with the fear of death. They marched alongside their allies, the Eldar, K'nib, Rashan and many other, attempting to end the tyranny and destruction caused by the beings known as star gods. The Krork had no system of religion or hierarchy, just the breeding cycles. The leaders were bred as leaders; no warrior could ever lead an army. Certain warriors could make it into the elite section of society, but it was quite rare.
The Krork and the Eldar often worked together or great projects, such as the Blackstone fortresses designed to destroy the C'tan permanently. They also shared access to the infinity circuit, a great meeting place for members of the two species. Eventually, with the falling of the Old ones and the encasement of the C'tan and the coming of the enslavers, the Krork were a dying race. Millions of their people were slaughtered and there was insufficient time for a new generation to be bred. So they also descended into tombs, like the C'tan, waiting for the Eldar to work their magic and create a new generation for them. Unfortunately, due to unforeseen circumstances, the Eldar never managed to recreate the Krork and so they remain in their stasis chambers, believing their race in good hands. Once they emerge and find their race still decimated, who knows what they will do. Most probably go on a mass rampage across the galaxy and eventual extinction.
There is a slight twist to this tale. Not all of the Krork descended into the stasis chambers. A few remained free and developed bio-mutation technology from wrecked Old One ships and databanks. They developed ways to extend their life and recreate their people. Unfortunately, in the process a rogue element working for the enslavers sabotaged the processes and altered the structure of the Krork, into the bestial Orks. They developed a war loving mentality and an obsession with danger. They began to reproduce rapidly and spread across the galaxy. Eventually, they began to fight amongst themselves and the Ork Empire collapsed down into many small fighting groups, as it is still to this day.
So with the coming of the Necrons, so come the Krork into a galaxy they nothing about, against people they don't know exist and with dwindling allies. Can they stop the tide of Necrons before it is too late or will they erupt into the galaxy and bring about another great slaughter of life, causing the cycle to being again?