Multiattack

The dragon attacks once with its bite and twice with its slam. In place of its bite attack it can use Rock Spire.

Bite

Melee Weapon Attack: +15 to hit, reach 15 ft., one target. Hit: 35 (5d10 + 8) piercing damage. Instead of dealing piercing damage the dragon can grapple the target (escape DC 23) and a Huge or smaller creature grappled in this way is restrained. While grappling a creature the dragon can't bite another target.

Slam

Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 8) bludgeoning damage and the target is pushed up to 10 feet away falling prone if it impacts a wall or other solid object. This attack deals an extra 9 (2d8) bludgeoning damage if the target was already prone.

Scouring Breath (Recharge 5-6)

The dragon exhales scouring sand and stones in a 90-foot cone. Each creature in that area makes a DC 23 Dexterity saving throw taking 70 (20d6) slashing damage on a failed save or half damage on a success. A creature that fails the save is also blinded until the end of its next turn.

Rock Spire

A permanent 25-foot-tall 5-foot-radius spire of rock magically rises from a point on the ground within 60 feet. A creature in the spires area when it appears makes a DC 21 Dexterity saving throw taking 18 (4d8) piercing damage on a failure or half damage on a success. A creature that fails this saving throw by 10 or more is impaled and restrained at the top of the spire. A creature can use an action to make a DC 13 Strength check freeing the impaled creature on a success. The impaled creature is also freed if the spire is destroyed. The spire is an object with AC 16 30 hit points and immunity to poison and psychic damage.