Deathmark

You target a creature within range that you can see and force it to make a wisdom saving throw. On a failed save, you choose one damage type and the target has a weakness to that damage type for 1 minute. This weakness stacks with any resistances, weaknesses or immunities it already has (Immunity becomes resistance, resistance becomes neutral, ect.) On a successful save, the creature is not affected and knows that something tried to affect it.