Cogwork Dragon

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

Magic Resistance. The dragon has advantage on saving throws against spells and other magical effects.

Clockwork Endurance. When reduced to 0 hit points, the dragon can choose to drop to 1 hit point instead. It can't use this feature again until it has finished a long rest.

Multiattack. The dragon can use its Steam Breath. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 25 (3d10 + 7) piercing damage.

Claw. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 17 (2d8 + 7) slashing damage.

Tail Swipe. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 19 (2d10 + 7) bludgeoning damage.

Steam Breath (Recharge 5-6). The dragon exhales scalding steam in a 60-foot cone. Each creature in that area must make a DC 19 Constitution saving throw, taking 54 (12d8) fire damage on a failed save, or half as much damage on a successful one.

The Cogwork Dragon 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 dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail swipe attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 20 Dexterity saving throw or take 15 (2d6 + 7) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.