Ecthar Alive and Immune After Finishing His Ghost, No Mechanics Available (Video)
When finishing Ecthar (1st boss of ghost of the deep dungeon) at the last second, the boss will respawn despite the animation going through. This leads to the encounter mechanics disappearing, and the exits staying blocked, thus leaving the boss unable to be damaged nor can you leave the encounter. Definitely frustrating that it happened on a solo flawless run.