Crystal Scorpion

Crystal Poison. If a target fails the DC 18 con save on the stinger attack, in addition to taking damage, it becomes afflicted with Crystal poison. It makes another CON save at the end of its next turns, until it either succeeds or until it has three fails. The original fail on the stinger attack counts as the first fail towards this total. Getting hit with another stinger attack and failing the save, does not count towards the total and does not start the "counter" of saves from new. The counter from the first and initial fail remains the active one. The DC for the save increase each time and are as following for the three saves: 18, 20, 22.

On a success the poison is overcome. On a third fail the creature becomes crystallized.

Crystallized. Condition. Works functionally the same as the petrified condition, with these exceptions:

A crystallized target is weak to bludgeoning damage. Each time it is hit with an attack that deals bludgeoning damage it must make a flat saving throw. On a 2-20 nothing else happens, except the damage. On a Nat 1 the creature shatters and is considered dead. From this death only a True Resurrection or Wish spell can revive the creature, as their body is only a pile of shards on the ground.

Multiattack. The Crystal Scorpion makes three attacks. Two with its claws, one with its stinger.

Claw. Melee Weapon Attack: +13 to hit, reach 5 ft., one target. Hit: 3d10 + 7 bludgeoning damage, the target is also grappled (escape DC: 20). Both claws can each grapple one, but only one, target at a time.

Stinger. Melee Weapon Attack: +13 to hit, range 5 ft. to the front, 10ft to behind the monster, one target. Hit:  2d8 + 8 piercing damage, the target must make a DC 18 CON save. On a fail it takes an additional 4d10 poison damage and is inflicted with Crystal Poison. On a success it takes half damage and is not poisoned.

Defensive Stance. The Crystal Scorpion enters a defensive stance, that lasts until its next turn, increasing its AC by 5 and gaining an additional reaction (for a total of 2). During this stance it can use its reaction for its Counter Attack ability.

Counter Attack. Reaction to being attacked by a melee attack (weapon or spell). Usable only when in Defensive Stance. The Crystal Scorpion shoves with its claws against an attacking creature. If no creature that is allied with the target, is within 5ft of the Crystal Scorpion, it gets advantage on the attack. The Scorpion cannot have disadvantage on this attack, no matter the circumstances.

Melee-Weapon-Attack: +13 to hit, reach 5ft, target: anything within 5ft in front of it

Hit: 2d10+8 bludgeoning damage. The target must succeed on a DC 20 DEX save or be knocked prone.

The Crytsal Scorpion can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Crystal Scorpion regains spent legendary actions at the start of its turn.

Claw (Costs 1 Actions). The Crystal Scorpion makes a Claw Attack.

Move (Costs 2 Actions). The Crystal Scorpion moves up to half its movement speed. This does not provoke an Attack of Opportunity.

Legendary Resistance (3/day). When the Crystal Scorpion fails a saving throw, it can choose to succeed instead.