GR unique boss invincible

Greetings, I was pushing a GR 75 and a yellow accursed mob pack spawned. I decided to pop a nemesis pylon as well spawning another pack of mobs. I killed them I thought but then out of nowhere an untargetable accursed mob that’s invincible ran up to me and hit me, killed me and then persisted. I had to run out of the GR level to avoid him.

As detailed in the stickied thread at the top of the forum…