Crystal Abomination

Immutable Form. The Abomination is immune to any spell or effect that would alter its form.

Infectious Gems. When a creature is hit by the Crystal Cannon or Flying Shards, the creature must succeed on a DC 12 Constitution saving throw or begin to be encased in green crystal, its speed is reduced to 0 and can only make an action or a bonus action. On the next turn the creature must succeed another DC 12 Constitution save or it becomes fully encased. While encased, the creature doesn’t need to breathe, eat, or drink, and it doesn’t age. The crystal takes full control over the body and they become a Crystal Infected. Nothing can break the crystal without killing the creature encased. A successful casting of the Dispel Magic spell on the crystal (DC 15) or exposure to direct sunlight destroys it. The crystal has 20 HP, AC 15 and minimum damage threshold of 10.

Multiattack. The Abomination makes two attacks: one with its Arm Blade and with its Crystal Cannon.

Arm Blade. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 17 (2d12 + 4) slashing damage.

Crystal Cannon. Ranged Weapon Attack 30 ft/60 ft: +7 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) piercing damage.

Hive Mind Strike. As a bonus action, the abomination can command a crystal infected to move up to 15 ft and take one melee action against a creature of 's choice.

Flying Shards. In response to a creature hitting the Abomination with a melee weapon attack, the Abomination deals 11 (2d10) piercing damage to the attacker.