Zach barely had time to shout before Mursoth's dagger pierced and broke his barrier, causing a lump to explode at the bottom of his throat. He stumbled half a step. Mursoth didn't stop as he pierced another barrier.
The others could tell what was happening. But they couldn't just turn around and flee when Zach was suffering from having his barriers break.
"Go! I'll be fine!" Zach saw their gazes. Running while Mursoth was breaking his barriers would be difficult. Soara and Yanael needed to be ready to fight.
He had to take down the barriers.
But the barriers were the only things stopping Mursoth and the avalanche of underworld energy from flooding the sewers. Since Mursoth had shown up, they had to give the sewers anyway. But they couldn't be in them when the underworld energy arrived.
Zach couldn't take down the barriers. His friends had to get out of the sewers first.