You burn away your life force in order to take your foe down with you.
A creature within range makes a constitution saving throw against your spell save DC. On a failed you and the target die instantly, on successful save the target takes damage equivalent to your hit point maximum, and you die
If you target a creature that is more than 1 mile away, you must be familiar with it, and must have met at least once.
Alternatively, if the target succeeds on the save instead of doing damage you can place a lifelong curse on the creature that can't be removed by any means short of a Wish spell.
Work with your DM to determine the effects of the curse and any special conditions to lift it. For example, you could curse a vampire to not gain a benefit from feeding until the curse is lifted.
Credit to Jim Butcher and the Dresden Files Series for inspiration.
* - When you would be reduced to 0 hit points.
Comments