Kosis the revelation

Encountered Kosis the revelation in t7 Augury with +1 level modifier with three emotions inscribed on waystone.

In one go at him i got him to 60% life, then he started doing his things and "sucked" back energy shield instantly to full. After that I couldn't do as much damage as in first attack - this time i couldn't get through energy shield. Then he charged the energy shield back again, and it seemed that with every insta-regen of energy shield the total amount of energy shield increased, as judging from the his ES bar, i was doing proportionally less and less damage than in previous damage window, up to the point that i was doing less than 5% in one go.

had to leave him alone. Please go and let him out, he must be hungry and sad now.

I noticed the same. Spent 15 minutes poisoning him to death because getting through his ES was impossible.

Not to mention his movements/actions appeared very bugged (he rarely acted or moved), and he dropped absolutely no loot.