My temporal warden has received the 'Impossible Death' achievement, but he's still alive. It was tough fight with boss accompanied by a lot of giants, pack of luminous horrors and rare ant-summoner. My warden was hit for more than 25% hp at once and it triggered the 'Guardian Unity' ability. Next turn this temporal clone received many hits from all mobs, he disappeared and 'Impossible Death' achievement was unlocked.
But warden managed to survive in this fight and have finally killed the boss with his minions.
