The Foot Stompaz are a small Ork tribe amongst the other small Ork tribes that combined to forge a mighty Ork WAAAGH! led by Warlord Gorgutz, who assaulted Lorn V, Kronus and the Kaurava System. It is common for Ork tribes to become part of other, larger Ork tribes if their Warboss is killed by another Ork leader.
Warlord Gorgutz used this method to quickly build a massive Ork invasion on three separate occasions; first on Lorn V, then Kronus and finally a massive assault was launched by these Greenskins upon the Kaurava System. However this also led to an easily fractured alliance amongst said clans.