The exchange he had with the Green Mantis made Damon realise something about his character, a defect that he allowed to go over his head.
Not until his fight with the Rank 4 Beast ended did Damon realise that he always fought and remained on the defensive throughout his battles so far, along with the disadvantages of it.
That was good for enemies that were weaker than him as he instinctively stuck to his [Tank] class. However, against formidable foes like the Rank 4 Green Praying Mantis, he was and will be forced to attempt to unleash his offensive skill, or risk losing the battle.
Thanks to the new item he received from defeating the magic insect, that weakness was addressed to an extent.
Now equipped with the green and black dagger named the Green Mantis Claw, Damon's offensive capability was upped.
