The Captain's Final Stand

Realizing there is no other way to survive, the user takes out their crystal, imbuing the rest of their mana and life force into a final effort to end whatever may come their way. The user, knowing there is no return for them, gives their life to do as much damage as physically possible.

The user cannot be knocked to 0 hit points unless damage would exceed their current hit points and their hit point maximum. All attack rolls made by the user will succeed on a 15 or higher and any roll that exceeds 20 can be considered a critical hit. The user will succeed all saving throws automatically. 

Once a minute passes, the user will begin to crumble to dust as their body and life force disappears as the rest of their life force goes into an unavoidable attack that fully disintegrates and kills the users target as well as anything within 500 ft. of the user, even if they are a God-like entity or an actual God. This will also occur if the users body becomes unstable or loses the ability to continue, i.e., the user dies before the time ends. They are unable to be revived by normal means and can only be revived through Godly intervention or the use of a Wish spell.