Black Cathedral WTF

What the **** is this ray of death in between boss fights? I cannot for the life of me figure it out. Any tips?

It's bug. Sometimes, if didn't kill boss fast enough, he activates crystals and they keep attacking you after boss is dead. Alongside with invisible boss; player stucking in the middle of the room and can't move; boss HP text and status not shown; player can't leave area if killed boss and died at the same time (it requires you to defeat boss that already dead). This encounter is very buggy right now, don't bring your HC characters.

yep. no hp, bugged all over