Astronomical Entombment

You invoke pale celestial energies to envelop around one creature you can see within range. That creature must make a Wisdom saving throw. On a successful save, the target takes 4d8 radiant damage, and the spell ends. On a failed save, the target takes 8d8 radiant damage, and the celestial energy forms an opaque 15-foot-radius sphere centered on the target that provides total cover. A creature that tries to enter the sphere takes 8d8 radiant damage and is shunted into the nearest unoccupied space outside the sphere. If the target is too large to fit in the sphere, the spell ends. Otherwise, the target is trapped in the sphere.

While the target is trapped in the sphere, it is blinded and restrained, and it takes 8d8 radiant damage at the start of each of its turns. A trapped creature may repeat the saving throw at the end of each of its turns. On a success, any subsequent damage this spell deals is cumulatively reduced by 2d8. Once the damage is reduced to 0, the spell ends.