The Orc Wars

The Orc Wars is the name given to the widespread uprising of orcish forces against the ancient Elven Empire, approximately 2000 years ago. These conflicts resulted in a large scale elven retreat from the Material Plane. However, the orcish forces were subsequently defeated by "the combined might of the humans, the halflings, and the dwarves."

Based on the party's discoveries at the Old Orc Encampment and associated demiplane, it seems possible that some or all of the orcish forces were supported by (or sought the aid of) the deity Silas.