All data comes from the test suit, and the final result is subject to the official suit.
tentative exploration
After inserting the key appears npc offers four buff options, according to the npc's dialogue, the player is helping the npc to catch the Dread Demon.
A camouflage buff appears on the head of the mob. (No special means are required to see)
Mobs with disguised buffs will transform into Dread Demon Kings when attacked.
NPC can allow switching buff, which can currently exist only one.
The part is not designed at the moment
The progress of the mob after the death of the Dread Demon King is enigmatic, killing one and adding 50% (it is estimated that the designer's decimal point key is broken again.) )
Although the buff has no time limit, it disappears when it dies, but it can be re-collected from npcs, and npc is in the copy mouth.
At present, BUFF is personal, and each person chooses their own.
When there is no bounty buff from the npc, the Dread Demon King is not visible.
After the destruction of the group, if the Dread Demon King is not dead, the monster that would have become the Dread Demon King will no longer change, and I am not sure if it is a bug.
The monster that becomes the Dread Demon King is currently fixed.