This skill it's something like passive.
When the player's life fall under 40 % He over power it's speed , damage , defence but he lose very fast his energy.
That's why this move it's dangerus.
If you put it at your charachter then you should be ready to face your enemy in an instant battle.
If the battle keep going for alot of time you will end up dead .
That's My Idea.
Thnx for read.