Kiss of the Succubus 2014

You kiss a willing creature or one you have charmed or held spellbound through spells or abilities such as dominate person. The target must make a Constitution saving throw. A creature takes 5d10 psychic damage on a failed save, or half as much damage on a successful one. The target’s hit point maximum is reduced by an amount equal to the damage taken; this reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

When you cast this spell using a spell slot of 6th level or higher, the damage increases by 1d10 for each slot level above 5th.