The monstrosity that was trying to break out of the gate was the mother Cerulean Cobra. Oliver was sure of it.
The thick, ivory white teeth that smashed the ground behind Fist King was its fang. The snake was too huge. So, it could barely put the fang through the gate to attack Fist King.
Still, a river of poison was squeezed out of the fang, drowning the bottom portion of the gate.
*Sizzle*
The extremely corrosive substance burned and dissolved the rock where it struck. Fortunately, the Mother Cerulean Cobra couldn't see them, hence couldn't target them with its long-range attacks.
And if it did, Oliver could imagine the pain he might feel just looking at the sizzling rocks, dissolving rocks.
Unlike normal people, his body would try to heal when he was injured. So, he would have to bear the acid-like poison-induced pain longer before he dies.
