Doom

You speak a word that alters the fate of a single creature you can see within 60ft, changing all possible paths towards a single, inevitable doom.

When you cast this spell, and at the start of your turn until the spell is complete, roll 5d10. Add the amount rolled into a pool, and add further rolls to the amounts rolled on previous turns. If at any point the creatures hit points are less than or equal to the value of the pool, the creature dies. Once the spell has begun casting, leaving the initial 60ft range or being transported to another plane of existence does nothing to halt the progress of the spell. The spell continues until the caster decides to end it, the caster loses concentration, the target is effected by a Remove Curse spell of 8th level or higher, or the creature dies.

A creature under the effect of the spell instinctively knows that failing to stop the spell will result in their demise.