Plan B is a contingency Kent devised before entering the forest. In the situation where he had to make a last-minute decision if his perfectly crafted plan was thrown into disarray, Plan B would come into play.
Obviously, he never expected there to be a hidden mechanism in this rotten world. He never expected such a deadly attack to come from nowhere.
However, as he narrowly evaded the spear, he knew he'd had to be careful, else his death would come faster than he hoped.
A little mistake can obviously cause a god's death in the most shocking ways.
So he abandoned the sword and took on the dragon claws, which Kent knew and was confident enough to face the immortals. His claws are gradeless, deadly weapons.
However, nothing prepared him for what happened next. The moment he activated 50,000 flame veins, something rather unexpected happened.
