ToME: the Tales of Maj'Eyal

First time I've ever seen this - no agent of the arena, level 7

upon seeing the title, i wanted to suggest the obvious, but...

was there some rare that randomly spewed AoE? there is a possibility that he died in a... "unfortunate", "accident"

Edit
was the "random mob spawning in place of fixed mob" issue resolved? because sometimes, if too many mobs spawn, the "fixed" npc is displaced, as it cannot spawn anynwhere but the designated area.
usually its something like the vault guardian going phase mode, but i guess it could happen in city as well.

AH and for the standards
-system
-steam or not
-version is in the title already (1.4.9)
-any mods?

happened again

please, can this be fixed DG?

If the Master of The Arena isn't flagged as invincible then it's possible that he was killed by Darkest Light interactions from NPC rares.