Mijin Gakure is completely different from any other one-hour ability, because it actually KOs the Ninja when it is used.
Ninja activate explosives on their own bodies, and give their lives to deal non-elemental magic damage to an enemy. It is a last resort used to protect information, allow allies to escape, or die with honor in a no-win situation.
The amount of damage is directly related to the amount of HP the Ninja has remaining, so if the Ninja has low HP, Mijin Gakure will deal little damage.
Any player that uses this ability will immediately be KO'd; however, no Experience Points are lost.
If the Innin ability is active, and a Ninja uses Mijin Gakure while behind an enemy, the ability will receive a damage bonus.