Dark Knight ability names

[Casper]

If tank is not at 100%hp when it wears they'd die is how I understood

Nah, the way it has been explained is:

You get a buff for 15-20 sec. If you take lethal damage, instead you stay at 1 and get placed in a living dead state (basically holmgang) for the remaining of the duration. At the end of the 15-20 sec, if you are living dead (got lethal damage), you get a debuff for 10 sec. If you reach 100% health at any point this debuff goes away. If you don't before it expires, you die.