For the last battle, the enemy has the skill Full Shield, which states that "The enemy will only receive the Damage of an Attribute when a group of 5 or more Runestones of that Attribute is dissolved (only dissolved Runestones will be counted)".

Does anyone know how can I deal damage to the enemy? I have tried dissolving 5+ water runestones but damage dealt is just 1. Is this a bug or am I doing something wrong?

Edit: Nevermind, I've figured it out. Damage dealt was too low, didn't break the defense.