Cold Curtain

You imbue a 20-foot cube centered on a point you can see within range with life-draining magic. When a creature first enters the space or starts its turn in the area, it must succeed on a Constitution saving throw or take 1d6 cold damage and have its maximum hit points reduced by the same amount. A creature whose maximum hit points is reduced to 0 dies. Once the spell has drained maximum hit points ten times, it ends. A creature can only recover these lost maximum hit points by spending at least 7 days doing the Recuperating downtime activity, or by a greater restoration spell or similar magic. When you cast the spell, you can designate creatures that it has no effect on, such as your servants or welcome guests.

At Higher Levels. When you cast this spell using a 5th-level spell slot or higher, the spell can drain maximum hit points an additional two times for every spell slot above 4th