Hello there!
Your mod is on a modpack called "Arcadia [RPG]" Which, has official multiplayer server on which i am opped
Sadly someone spawned a doppleganger in the spawn of the server.
The command that i used to try and kill the boss was the following:
/kill @e[type=darkdoppelganger:dark_doppelganger]

Tho it did kill the main boss, the minions did not disapeared

Found a fix :
Command was

/data modify entity @e[type=darkdoppelganger:dark_doppelganger,distance=..128,limit=1] Health set value -1.0f

Hello I also found this same loophole for minions to not die, I have fixed 1.21 version I plan to fix 1.20 asap with same fix !

Hello I also found this same loophole for minions to not die, I have fixed 1.21 version I plan to fix 1.20 asap with same fix !

Many Thanks !

ive moved the minions to there own config and entity so they are now killable no matter what!