Bind to Crystal

You attempt to trap an Elemental that you can see within range inside a crystal. It must make a charisma saving throw or be trapped within the gem. if it has a challenge rating above 5, it gains +2 to this saving throw for every challenge rating above 5 it is. If the spell is cast at a level above 4th, this +2 bonus per challenge rating only begins at a challenge rating two higher than the level of the spell. However, if the target of the spell is a high enough challenge rating to begin getting the +2 bonus to the save, it gains the bonus as if the spell were simply cast using a 4th level spell slot. The target also gets a +5 bonus to the saving throw for every elemental already bound within the gem.

A creature in possession of the gem can do one of the following things as a bonus action:

Release: The elemental materializes in an unoccupied space that the holder of the gem can see within 60 feet of them.

Recapture: If the elemental is within 60 feet of the holder of the gem, it is trapped back within the gem. Otherwise, it is pulled directly towards the gem a number of feet equal to the level of the caster who originally bound the elemental within the gem.

Locate: The holder of the gem magically known the elemental's location.

Command: The holder of the gem issues a verbal or telepathic command to the elemental. If the holder of the gem is the one who originally bound the elemental, the elemental must obey. Otherwise, the elemental must make a charisma saving throw (15 + the gem holder's charisma modifier + their proficiency bonus) or obey the command.

Unleash energy. The holder of the gem releases a portion of the elemental's energy, if it is in the gem. The elemental loses 10 hit points, and an effect takes place, depending on when element the elemental is affiliated with.

            Fire: Flames erupt in a 30-foot cone. Each creature in the cone must make a dexterity saving throw (DC 10 + the elemental's constitution modifier + its proficiency bonus) or take fire damage equal to 3 times the elemental's challenge rating, and flammable objects in the area of the cone are set ablaze.

            Water: A jet of water slams outwards at a creature within 30 feet of the gem. Make a ranged spell attack using the elemental's stat block, using constitution as the spellcastig ability score. On a hit, the target takes bludgeoning damage equal to 3 times the elemental's challenge rating, and must make a strength saving throw (DC 10 + the elemental's constitution modifier + its proficiency bonus) or be knocked prone.

            Earth: A shockwave emanates through the ground within 30 feet of the gem. That ground becomes difficult terrain until the beginning of the next turn of the holder of the gem; for every 10 feet a creature moves in this area, it must make a dexterity saving throw (DC 10 + the elemental's constitution modifier + its proficiency bonus) or fall prone.

            Air: Rushing wind blasts from the gem in a 60-foot line that is 10 feet wide. Each creature in the line must make a strength saving throw (DC 10 + the elemental's constitution modifier + its proficiency bonus, with advantage if the creature is only partly in the line, and disadvantage if it is flying) or take thunder damage equal to 3 times the elemental's challenge rating, and be forced 20 feet directly away from the gem.

An elemental inside the gem regains 1 hit point at initiative count 20 on each round, and its attacks against the holder of the gem or the creature who bound it deal minimum damage. The elemental is freed after a number of days equal to the caster's level, or if it drops to 0 hit points. In the latter case, it is freed with 1 hit point remaining.