Guild Wars 2

It’s the historian and the new Toxic Alliance debuff, I think Toxic Pollen.

SHort summary:
Pull the priestess to the historian (this can happen naturally if your group is small and retreats…). HIstorian tanks the priestess. Gets the debuff. Priestess dies. Historian acts a little odd (halucination effect) and then vanishes (dies? No death animation)

From there, the temple is glitched. and won’t recover without restarting the server instance.
//Portable Corpse

Historian says “Retreat!” and then uses a vanishing skill.

The bug that was supposedly fixed in July has returned.

He’d been dying in AoE from the mobs that lingered a moment.

Now he’s dying from an effect thats tied to living story.
Honestly, just make the historian resurrectable. Then, no matter what kills him, new content, rock from the sky, or Zhaitan’s sneeze, we can bring him up and continue.
//Portable Corpse

Yamagawa.5941:

He’d been dying in AoE from the mobs that lingered a moment.

Now he’s dying from an effect thats tied to living story.
Honestly, just make the historian resurrectable. Then, no matter what kills him, new content, rock from the sky, or Zhaitan’s sneeze, we can bring him up and continue.
//Portable Corpse

That wouldn’t necessarily help. It’s not unusual for NPCs to die, get resurrected and then fail to continue with what they were supposed to be doing. Giving him Determined and set to avoid combat would be better.

Well, we have two general paths here.

Path a) make the NPC immune to each kind of effect that might kill it. Evidence is that this only works so long as the NPC is never exposed to new content, like Toxic Alliance Debuffs. oops. The term here is “Brittle”.
Path b) make it so that the NPC can legitimately die, like 100s of other NPCs in the game, and then be revived to continue the mission. The term here is “Robust”.

Robust solutions do usually need more setup effort (making sure the event chain does not stall when the NPC dies, making him despawn anyway, making sure the NPC has a working reset routine for when he dies, etc…), but long term are low maintenance and low downtime, compared to brittle solutions.

//Portable Corpse