End of Days

A sphere of negative energy ripples out in a 120-foot-radius sphere from the caster, swirling necromantic energy draining the life force of all creatures for one minute. Each creature in the area when the spell is first cast must make a Constitution saving throw, and any time a creature begins its turn in the area after it must repeat the save. A target takes 12d6 necrotic damage on a failed save, or half as much damage on a successful one. Additionally, on a failed save the target's hit point maximum is reduced by a number equal to the damage taken, and the target cannot regain hit points by any means until the start of their next turn. These effects can only be undone by the use of Greater Restoration, Wish, or similar magic.

After the initial casting, the damage of this spell is reduced to 4d6.

Every round after the initial casting of this spell, additional effects begin:

Round 2-5: Green tendrils of necromantic energy sprout from the sickly ground, and all creatures in the spells radius must make a Dexterity saving throw, or be restrained until the start of their next turn.

Round 6-8: The necromantic energy becomes sickeningly strong, and begins to truly drain the life of the creatures within. All creatures not totally immune to necrotic damage must make a constitution saving throw, or suffer the effects of the Slow spell.

Round 9-10: A sphere of condensed necromancy forms just above the caster, and all other spell effects end. Instead, for the last two rounds any damage dealt by the spell is converted directly into healing for the caster.