The Sea of the East was the large ocean separating the Angarak continent of Mallorea from the unnamed continent that contained the Alorn, Western Angarak and unaligned nations featured in the Belgariad and Malloreon.
It was formed at the climax of the War of the Gods, when Torak used the Orb of Aldur to prevent the forces of his brother deities from exterminating the primitive Angarak people. He split the proto-continent in half, creating a vast canyon behind his forces as they retreated, which was then flooded.
During Enchancter's Endgame, part of the strategy of the allied Western nations was to put a Cherek fleet into the Sea of the East. This would cut off Mallorean reinforcements to Emperor Zakath's invasion of Cthol Murgos, as part of a broader campaign to distract Angarak attention from Garion's infiltration of Cthol Mishrak.