Orcs are not too religious. War and hunt are more interesting for them, than deference to unknown essences with questionable results. They are used to achieve everything by themselves and to get their prey in battle, so they serve to resolute gods.
Beast Khar - god of chaos and destruction, which well educated elves think is the demon from lower world. For a long time orcs had blood treaty with Khar, concluded by great orcish leader - Zurdag, for the help of dreadful god. This treaty was severed when final Khar's embodiment - Rakgul the Destroyer - rose against and banished him. Rakgul's death put an end to demonic invasion, so Khar's power on souls of orcs ended, but, many orcs still call the Beast in the battle, and sacrifice blood of their enemies to him.
It is considered that it is him, who taught shamans of orcs fundamentals of destroying magic.
Kar-hor, Father of ravens - the most ancient god respected by all orcs. It is Great steppe of Father of ravens where souls of fallen heroes go, it is he who will gather army of dead ones for the final battle, when the sun will go out and stars will fall from the sky. There are no sacrifices and altars to the Father of ravens - because he can call everyone in any moment when he wants, and he will, when the time will come. Battlefields are altars to the Father of ravens.
Raven is the servant of Father, and his messenger, kill the raven - and you'll incur anger.
Father of ravens considered as the author of orcish runic language and counting, creator of mechanical arts and first hunter tamed the wolf.