The inside of his mouth had been pierced by a pillar of metal.
Maybe if Zaroth used all of his strength, he would be able to move with enough force to break free.
But then what?
Moving away would mean two things.
First, the three wounds he had recently received would begin to bleed. That, coupled with the fact that one of his arms was cut off, would cause him to lose too much blood too quickly, dying in the process.
And second, if he didn't die, let's say he used the last of his mana on firebreath or fireballs to close off his wounds, giving him more time—then what?
He would be damaged, without his beasts, without his arm, without his mana, and away from his opponent, who could just spam him with attacks from a distance.
Zaroth would not be able to do anything, and he would lose.
So, this wasn't an option.
If retreat wasn't possible, one had only one option,
To go forward.