Died with "health" left on Map Tier 11

Running a Stormweaver Archmage Fireball build with converting all my HP and ES to Mana and letting damage draining my mana first. While having no spell or item equipped which could potentially drain from my health I still died to something while running a Tier 11 Map while still having some Mana left.

Sadly I can't recall the modifiers on the waystone to verify it as a bug (might be a feature). Just happened this one time though.


It would be great to have a "killed by..." feature!


Edit: Happened a second time now, maybe somethings off with dmg calculation or gaining Mana after being dead by stray spells still existing after death?