The Erebus is a Dungeon of the Enchanted Forest accessible through the NPC Guardian of the Forest, on the north part of the map. All the party members must be at least level 95 and possess the Stone of the Dryads to enter inside the Dungeon.
As soon as you start the Run you have exactly 15 minutes to clear 3 waves of monsters and the final boss: Bagjanamu.
If you get killed more than 2 times you are out of the Dungeon for 3 minutes.
Bagjanamu can't regen his health but he has 4 Healers, one on each corner, that cyclically respawn. If left alone too long the healers can fully replenish Bagjanamu's health.
As every monster on the map Bagjanamu is weak to Devil.