Over the course of 10 minutes, you entomb a creature you can see within range in a deep steel sarcophagus. The spell automatically fails if the target moves out of range while its still being cast.   The sarcophagus can not be opened until the spell ends. While inside the creature enters a coma-like state during which it becomes completely immortal.
The spell ends when the sarcophagus is destroyed or the creature is removed.   Ascended Spell. This spell costs 2 Spell slots to cast. A 7th-level spell slot and a 6th-level spell slot.