Dagon was a major northwest Semitic god, reportedly a god of grain and agriculture, worshipped by the early Amorites, by the people of Ebla and Ugarit, and a major god, perhaps the chief god, of the Biblical Philistines, demonized by ancient Israelites.
In many campaign settings for the Dungeons & Dragons fantasy role-playing game, Dagon is a demon lord, also called Prince of the Depths. His realm is the 89th layer of the Abyss, and is known as Shadowsea. Dagon is an obyrith.