Manannan

Manannan mac Lir, or 'He of the Isle of Man, son of the Sea' is the Irish sea God. He is said to ride over the waves in His chariot in the same way mortals ride over the rolling hills. He rules over the realm of Emain Ablach, the Otherworldly Isle of Apples, commonly associated with the Isle of Man, though it has obvious parallels with Avalon of the Arthurian cycle.

Manannan is a shapeshifter and a bit of a trickster, as befits a sea God. He is also a warrior and a great magician. His Welsh parallel is Manawydan fab Llyr.

I've shown Him here with triskeles, the emblem of the Isle of Man, on His cloak, as they resemble the waves of the ocean. I've also given him the little red dots seen on some figures of later Celtic manuscripts, such as the Book of Kells.