Clock work Archmage

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

Spellcasting. The archmage is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 19, +10 to hit with spell attacks). The archmage can cast disguise self and invisibility at will and has the following wizard spells prepared:

Cantrips (at will): fire bolt, light, mage hand, prestidigitation, shocking grasp

1st level (4 slots): detect magic, identify, mage armor, magic missile

2nd level (3 slots): detect thoughts, mirror image, misty step

3rd level (3 slots): counterspell, fly, lightning bolt

4th level (3 slots): banishment, fire shield, stoneskin

5th level (3 slots): cone of cold, scrying, wall of force

6th level (1 slot): globe of invulnerability

7th level (1 slot): teleport

8th level (1 slot): mind blank

9th level (1 slot): time stop

*The archmage casts mind blank, stoneskin and mage armor spells on itself before combat.

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

Dagger. Melee or Ranged Weapon Attack: +6 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 16 (1d4 + 15) piercing damage.

Bite. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 19 (2d10 + 8) piercing damage plus 9 (2d8) acid damage.

Claw. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 15 (2d6 + 8) slashing damage.

Tail. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 17 (2d8 + 8) bludgeoning damage.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 19 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

Clockwork ejection when it drops to 0 hit points the clockwork dragon will eject its mortal companions golem form. during this time the companions form will carry the soul gem and be able to attack as a separate entity to protect the clockwork dragon.

 While the clockwork dragon's body is at 0 hit points, the dragon cannot be active for the next 24 hours. The companion must return to the dragon's body within 2 hours or both will be destroyed. Once both bodies are rejoined the dragon's body will be paralyzed until it regains 1 point of health. After spending 1 year in its paralyzed place with 0 hit points, it regains 1 hit point. 

Breath weapon (charge 5-6) The clockwork dragon uses one of these breath attacks per charge

Acid Breath  The dragon exhales acid in a 90-foot line that is 10 feet wide. Each creature in that line must make a DC 19 Dexterity saving throw, taking 67 (15d8) acid damage on a failed save, or half as much damage on a successful one.

Slow Breath The dragon targets one or more creatures it can see within 10 feet of it. each target must make a DC19 wisdom saving throw against the magic. On a failed save a target can't use reactions, it's speed is halved, and it can't make more than one attack on its turn. In addition, the target can take either an action or a bonus action on its turn, not both. These effects last for 1 minute. A target can repeat the saving throw at the end of each of its turns, ending the effects on itself on a success.

Clock work Shadow Breath. The dragon exhales shadowy acid in a 90-foot line that is 10 feet wide. each creature makes a DC 19 dexterity saving throw taking 67(15d8) nectrotic damage on a failed save, or half as much damage on a successful one. A humanoid reduced to 0 hit points by this damage dies, and a shadow gem forms from the the corpse and after one round forms 1d4 golem (1, clay, 2 flesh from the flesh of the corpse creating undead, 3 iron, 4 stone golem) acts immediately after the dragon in the initiative count. The golem is under the dragon's control 

The Clockwork Archmage can take 2 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 Clockwork Archmage regains spent legendary actions at the start of its turn.

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

Slow breath the dragon makes a slow breath attack using two actions