Multiattack. The dragon makes three attacks: Two with it's sharpened maw and one with it's claws

Sharpened Maw. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 15 (2d10 + 4) slashing damage.

Claws. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage.

Disembody (Recharge 5–6). The dragon heats up it's sharpened maw, and targets one creature it can see within  10ft of it. The target must make a DC 14 Dexterity saving throw, taking 36 (8d8) slashing damage on a failed save, or half as much damage on a successful one. If the saving throw fails by 5 or more, the target instead takes 64 slashing damage, and loses an arm or a leg.

Parry. The Sickle Mouth adds 3 to its AC against one melee attack that would hit it. To do so, the Sickle Mouth must see the attacker.

Riposte. The Sickle Mouth makes a Sharpened Maw attack against a creature that's missed it with a melee attack within range.