Athtar (Ashtar, 'Athtar, Atra of the sky) 'the terrible' is a son of Athirat. He may have been a god of the desert or of artificial irrigation. He loses his kingship to Yam. He complains to Shapsu about his lack of status. When Baal dies, Athtar tries to take his throne, but doesn't fit, so he becomes king of the earth.
Source: Christopher Siren's Canaanite Mythology FAQ