Finally finish with new mechanic "Stagger". When the boss run out of stamina, they will be staggered. Player has around 6.5 seconds to attacks the boss and stack up stagger bonus then click at the button on the top left to activate Stagger Finisher.
Each skill attacks add unequal increase %bonus but mostly skill with more hit the better.
Stagger Finisher damage is equal to parry x bonus%. It's a free attack no stamina or SP/MP consume. If you stack enough SP/MP + finisher, this can deal 25-30% of boss's HP. This %HP loss is already boss with Max HP increased. It's deal around 50% of boss's HP so, I have to increase their HP.
Now, I will go back to continue on Tentacle Bind animation.