SPAWN
Stronger than ordinary bosses and with better rewards, these bosses respawn every Monday on CH1 every few hours. Time to respawn can be seen from the dungeon page (ctrl+d)
When these bosses are defeated a large number of npc chests will spawn and to be able to open these chests you must have constantly attacked the boss with a few thousand damage / hit as a safety measure. If for various reasons you need to take a break from attacking, it should not be longer than 30 seconds.
INFO
This bosses does not drop items, the drop is from opening the boxes: