Ancient Gem Dragon

Multi-Action Randomizer. The Animated Gem Dragon has between 1-2 attack actions per turn. This is determined by a d6 roll at the start of its turn.
1-4 = 1 Action; 5-6 = 2 Actions

Ancient Fortitude. If the Animated Gem Dragon is within 30 feet of the gem and on a rocky floor, they are able to use its bonus action to regain 1d20+5 HP.

Protector of Gems. The Animated Gem Dragon will lose its flight capabilites if its not withing 50 feet of the gem and it will lose its magic capabilities when it isnt within 30 feet of the gem. If the dragon loses flight it will plummet to the ground go prone and get 2d12+6 true damage.

Mythical Rage. If the players destroy the gems. The Animated Gem Dragon will go into raged mode gaining mythical action aswell as +2 attack bonus and regaining 2d20+10 HP as it sucks up the remnants of the crystal. If the gem ceases to exist the Dragon won't gain bonuses, yet he will still unlock the mythical attacks.

Spellcasting. The Animated Gem Dragon is a 10th-level spellcaster. Its spellcasting ability is intelligence (spell save DC18 , +10 to hit with spell attacks). The Animated Gem Dragon has following Wizard spells prepared:
Cantrips (at will): Mold Earth, Mage Hand
1st level (4 slots): Earth Tremor, Hellish Rebuke
2nd level (3 slots): Dragon's Breath, Shatter
3rd level (3 slots): Erupting Earth, Wall of Sand
4th level (3 slots): Fire Shield, Summon Construct
5th level (2 slots): Transmute Rock, Modify Memory

Claw Swipe. Melee Weapon Attack: +12 to hit, reach 5 ft., 5 feet cone. Hit: 16 (5d4 + 6) slashing damage.

Mouth Spike. Ranged Weapon Attack: +12 to hit, range.30/50 ft., 1 target. Hit: 18 (3d8 + 6) piercing damage.

Screeching Stone. Aoe Attack Con save DC19, range. 25 ft., on a fail the target will take 18 (4d6 +6) psychic damage and be defeaned for 3 rounds and have disadvantage on spells with a vocal component.

Spiked Thrust. The Ancient Gem Dragon flaps its wings making 3 stone spikes thrust out and fly towards the enemies. You can choose to target the same creature or up to 3 creatues. They have to do a DC 16 Dex save and on a fail recieve 3d8+6 damage.
After this Bonus Action is used the Dragon will recieve 3d4 true damage.

Winged Parry. If the Animated Gem Dragon is hit by a meele or spell attack he can use reaction to increase his ac by +3. If he nullifies the attack he will either redirect the magic attack back to the caster or repost and use a claw attack against a meele attack.

Total of 2 Legendary Actions.

Magical Flight (Costs 2 Actions). The Dragon flies up 15 feet into the air. His base movement will also be his base flight speed. This lasts for 2 turns.

Stoned Resistance (Costs 1 Action). The Dragon uses his magical Rock skin to automatically succeed a saving roll.

Mythical Actions can only be used if the gem gets destroyed or vanishes:
Total of 4 Mythical Actions (Only restores after a short rest). Using a Mythical Action will use up all actions for that turn.

Tomb of Rocks (Costs 2 Actions). The Ancient Gem Dragon does a screetch, making metal spikes and magma spike out of the ground. Everything within 30 feet besides the Dragon has to do a DC 21 Dex Save or take 28 (4d8 +12) piercing and 14 (2d8 +6) fire damage.

Magma Blast (Costs 1 Action). The Ancient Gem Dragon creates a orb of magma in its mouth and spews it out in a straight 50 feet line. Everything in that line takes 22 (2d10 + 12) fire damage.

Possible if he imbued the gem: (loses +2 to hit and sacrefices 20 HP)
Gems Magical Infusio. The Ancient Gem Dragon vaporizes the gems imbued into itself and in return adapts all its magical energy, gaining 3 9th level spell slots.