Emperor of Corpses boss dealing damage through ward

The red pulsing ground DoT during the boss fight is dealing damage directly to my health bar while I had 3-4k ward. I was wearing Exsanguinous, Last Steps of the Living, and the experimental ward generation gloves. I didn’t record the run that I died in but I do have a clip of it happening during a successful run after.

https://imgur.com/a/CtTmpvG