Sorcerer/18th

Final Form

Starting from 18th level, if you are reduced to 0 heart points but not killed outright, then at the start of your next turn you are brought back to 1 heart point, and you can expend any number of magic points to regain 5 heart points for each magic point spent in this way. If you were brought to 0 heart points by another creature and then expended at least 10 magic points, for 1 minute that creature has disadvantage on all saving throws against spells you cast, and all spell attack rolls you make which target that creature have advantage.

Once you are dropped to 0 heart points, you must finish a long rest before you can again enter your Final Form.