The Demon Sea (Japanese: 魔海 Romaji: makai; also be seen in the TV series as DmonS Ocean and Damanss Seals) is a large circular ocean in the center of the Slayers world.
The peninsula where much of Slayers is set is bordered to the south and the east by the Demon Sea. Deep Sea Dolphin anchored the west corner of the mazoku barrier in the Demon Sea until the barrier fell following Hellmaster Fibrizo's destruction.
The Demon Sea was formed by the battle between Flare Dragon Ceifeed and Ruby Eye Shabranigdu during the Shinma War. The middle of the Sleeping Dragon continent was turned into a massive crater by their battle; the crater then filled with water, becoming the Demon Sea. This former battleground of the mazoku and shinzoku leaders resides at the center of the ocean, and is considered forbidden to the servants and subordinates of both, according to Xelloss. The Pillar of Light, which was built upon it by the servants of Night Dragon Vorfeed, became visible from the peninsula in Slayers TRY.
Another significant location in the Demon Sea is Wolf Pack Island, which is located to the south of the peninsula and which is where Greater Beast Zelas Metallium anchored her corner of the mazoku barrier.