Ash Crawler

Petrifying Gaze. If a creature starts its turn within 30 feet of the Ash Crawler  and the two of them can see each other, the Ash Crawler can force the creature to make a DC 12 Constitution saving throw if the Ash Crawler isn't incapacitated. On a failed save, the creature magically begins to turn to stone and is restrained. It must repeat the saving throw at the end of its next turn. On a success, the effect ends. On a failure, the creature is petrified until freed by the greater restoration spell or other magic.

A creature that isn't surprised can avert its eyes to avoid the saving throw at the start of its turn. If it does so, it can't see the Ash Crawler  until the start of its next turn, when it can avert its eyes again.

If it looks at the Ash Crawler  in the meantime, it must immediately make the save. If the Ash Crawler  sees its reflection within 30 feet of it in bright light, it mistakes itself for a rival and targets itself with its gaze.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) piercing damage plus 7 (2d6) poison damage.

Fire Breath. The Ash Crawler exhales fire in a 60-foot cone. Each creature in that area must make a DC 21 Dexterity saving throw, taking 63 (18d6) fire damage on a failed save, or half as much damage on a successful one. Anything flammable hit by this sets on fire. 

Fire Tail. A Ash Crawler swings it's tail around in a 20 foot radius around itself. Setting anything flammable on fire. Anything hit takes 4d6 Fire damage. 

Poison Spike. A Ash crawler makes a spike of Poison come from it's tail. It flies 60 feet and Poisons the target. It deals 1d6 Poison damage per turn they are Poisoned. The Poison lasts until they succeed a DC 16 Constitution saving throw. The spike impales the target and the Poison doesn't stop until it's removed. Doing so deals 3 damage to the person per turn as the begin to bleed as well. Bleeding can be stopped using an action. 

Acid Spit. The Ash Crawler Spits Acid at a target, this acid is corrosive as well as acidic. If metal is hit with it, it gets -1 to it's effectiveness. If it's effectiveness hits 0 it corrodes completely. It deals 4d6 Acid damage to a target. 

Tactics of Ash. When an Ash Crawler attacks a creature within 10 feet on you, and hits. You can attack it as a bonus action, even if you already have as a bonus action. This means if Ash Crawlers flank you, you are likely dead.

Fire Healing. When in fire or hit by it the Ash Crawler heals the amount of damage it does and moves twice as fast for that turn. 

Poison Immunity. When hit by Poison negate it. 

Acid Reversion. When hit by Acid begin regenerating. You heal 20 HP for four turns when his by acid. 

Ash. When attacking a Ash Crawler in Melee you must make a DC 16 Constitution save or begin to choke. This is because you are breathing in ash. This Ash is burning hot. You take 4d6 Fire damage each time you attack an Ash Crawler in Melee. 

Convergence of Ash. When an Ash Crawler dies it turns into a Gem filled with Ash. This Gem is Cursed and if it's crushed the Ash Crawler dies. if not it can regenerate after 3 turns back into an Ash Crawler. This makes them especially hard to kill. 

Cocoon of Transport. An Ash Crawler can kill itself to turn back into a Gem so a Ash Crawler Queen can eat it and release hundreds of them in silence to make Chaos when they revert back into Ash Crawlers.