WAAAAAAAAGH!
Warboss Grimskull is the Ork Warboss leading the Waaagh!, he has been quite successful, and has conquered several planets before the invasion of Graia. Grimskull is extremely cunning, making his horde unusually well-organized and very dangerous.
The Warboss is the biggest, strongest and most cunning Ork in a Waaagh! , getting the best armor, weapons and wargear available in his horde. The longer any Ork lives and the more it fights, the larger it gets. Upon brutally establishing itself as leader, a Warboss grows even larger with each success