You unleash virulent magic on a creature you can see within range. The target makes a Constitution saving throw. On a failed save, it takes 14d6 Necrotic damage, and its Hit Point maximum is reduced by an amount equal to the Necrotic damage it took. On a successful save, it takes half as much damage only. This spell can’t reduce a target’s Hit Point maximum below 1.
RollQuest ships the D&D 2024 SRD as a content pack, on a 5e character sheet that does the maths - roll from the sheet and let the numbers work themselves out. Free to start.