Got hit by Urkis, the High Tempest for 270 points of lightning damage (I had 67% resist) AND by a thrown boulder for 130 points of damage in one turn. I had a total of 600hp and was not anticipating such a spike. I wasn't watching my HP carefully and should've shielded when below 50% hp. But more importantly, I wasn't watching the number of enemies on screen who can hit me. I didn't anticipate the boulder.

Luckily, I had the Blood of Life effect.