The Mazoku barrier (Japanese: 神封じの結界 Romaji: kami fūji no kekkai; lit. "the god-sealing barrier") was a magical force-field which had completely sealed off a portion of the land around as big as Europe in the Slayers world.
The barrier was erected by the mazoku during the Kōma War, to prevent the other subordinates of Flare Dragon Ceifeed or their servants from interfering while the mazoku battled Aqualord Ragradia and the dragons under her command. It required great amounts of energy to maintain, which was supplied by Greater Beast Zelas Metallium, Deep Sea Dolphin, Dynast Grausherra and Hellmaster Fibrizo, each of them stationed at strategic positions around the barrier. After the war, probably because of the conflict's uncertain outcome, the force-field remained in place, at least until the destruction of Hellmaster a millennium later. Some suspect that it disappeared somewhat sooner, as Fibrizo left the Desert of Destruction earlier in order to carry out his plans of destroying the world, which later caused his downfall.
- The anime representation of the barrier had some mistakes, as three of the symbols where missplaced. The top up is Greater Beast's, while it should be Dynast's; the top down is Dolphin's, while it should be Greater Beast's; and the top left is Dynast's, while it should be Dolphin's.