Sources: Player's Handbook
Gruumsh, chief god of the orcs, is chaotic evil. His titles are One-Eye and He— Who-Never-Sleeps. Gruumsh calls on his followers to be strong, to cull the weak from their numbers, and to take all the territory that Gruumsh thinks is rightfully theirs (which is almost everything).
The domains he is associated with are Chaos, Evil, Strength, and War. Gruumsh’s favored weapon is the spear. He harbors a special hatred for Corellon Larethian, Moradin, and their followers. In ages past, Corellon Larethian put out Gruumsh’s left eye in a fight.