Please check Taken Blights.
Seasonal Grandmaster Whisper conqueror challenge is next to impossible as Taken Blights can't be destroyed, stepping into one (first room) means insta death.
Funny or not funny enough the Taken public event in the Dreaming City suffers from the same bug or feature just to a less extent. Here it takes about 3s to be killed by just running into/standing in a Blight.
Intentional?
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I encountered the same bug. Even at max/200 health in a Well of Radiance, I'd die within 2 seconds. Luckily, you don't actually have to destroy most of the blights. Just one near the end, as it blocks the door to the boss room. You just have to stand on top of it and destroy it from above, then jump off at the last second. It still needs to be fixed, as that mission is not completable by the average player.