Cursed Slumber

Choose a creature you can see other than a construct or undead within range. It must make a Wisdom saving throw. The target takes 20d10 psychic damage and is stunned until the start of your next turn on a failed save or takes half as much damage and can’t take reactions until the start of its next turn on a success. This damage can’t reduce the target below 1 hit point. If the target is reduced to 1 hit point and has an Intelligence of at least 5, it falls unconscious, sleeping with no need of food or water (although it must still breathe) until the spell is dispelled. No violence, face-full of water, or kiss will wake the target of the cursed slumber. The target continues to age normally and can die of old age.
If the target remains asleep for at least 1 year, the spell grants benefits to spellcasters in its vicinity. Each creature within 30 feet of the sleeping target has advantage on Intelligence (Arcana) checks. Treat the slot level of any spell cast within 30 feet of the sleeping target as one higher if the target has been asleep at least 1 year. Effective slot level increases from multiple sources are not cumulative.