The boss disappears on the start of battle and won't return until all the adds that are alive when she goes, die. This is a bad bug since you can one shot the whole group with a pull mechanic when she disappears without the return requirement. There is a reset option, going up the stairs around the pillar in the other room then come back down, that puts you out of range and will reset. However, the bug remains. A better solution would be to have the boss not show up initially, but have the mobs show, then when they die the boss shows. Or, not have the boss disappear at all and just have her and the mobs attack the player. For some reason most of the mobs die from the boss at the start, which is very weird. please fix the bug