Essence Prison

You drain the life force of up to 10 creatures within a 30 foot diameter cylinder, 20 feet tall. As part of the casting, you draw an arcane circle enclosing all the targets and the gem. Upon completion of the casting, all targets must make a Constitution saving throw. On a failed save, their essence is stolen from them and trapped within the crystal. On a failed save, their maximum hit points are reduced to 25 percent of their maximum, rounded up, and their ability scores are reduced by 3. In addition, any memory they have of the caster is lost. On a successful save, their maximum hit points are reduced to 75 percent of their maximum, rounded up, and their ability scores are reduced by 1, but they retain their memories, and the gem does not store their essence. These reductions can only be reversed by a casting of Wish, or a 9th level casting of Greater Restoration. Regardless if they succeed or fail the saving throw, and all targets suffer a point of exhaustion. A creature can only be targeted by this spell once. Regardless if they succeed or fail, a targeted creature is immune to its effects for the rest of their lives. This spell cannot target Undead or Constructs.

As an action, you can crush the gem in your hand to absorb the essence stored there. You gain the hit points contained within, increasing your maximum hit points for 7 days. In addition, you gain a temporary +2 bonus to your ability checks and saving throws for 1 day per creature affected by the spell.  Finally, your vitality is restored, and you gain an extension to your lifespan equal to 20 years for each creature targeted, and your aging is halted for those years. 

You may only have one essence stone at a time created in this way. If you cast the spell again, the new stone is formed and the current stone shatters and its stored essence is lost.