Trial of the Sekhemas

I played a Trial of the Sekhemas forth floor and got the minor boon "You can´t be damaged until you complete the next room" as a reward in the last room befor the boss from a merchant.
While it worked for most of the bosses abilitys, with the one where he teleports in the middle of the arena and spins while shooting lightnig I still got damaged, I didn´t loose honer but i lost ES