Constructed Nature. The construct does not require air, food, drink, or sleep.

First Layer Resistance. While the construct has 200 hit points or more it takes 10 less damage from weapon and spell attacks.

Second Layer Thorns. While the construct has more than 100 hit points but under 199 hit points, creatures making melee attacks against the construct must make a DC 19 dexterity saving throw or take 11 (2d12) force damage.

Third Layer Destroyer. If the construct has below 99 hit points its speed increases by 20 ft., its attacks do an extra 3 (1d6) force damage, its armor class increases by 2, and it regains 10 hit points at the start of its turn if it has at least 1 hit point but the amount does not exceed 99 hit points.  

Specialized Absorption. If the construct takes force, fire, or radiant damage it instead takes no damage and regains hit points equal to 2 times the amount of damage inflicted and gains the benefits of a lesser restoration spell.

Spellcasting. The construct is an 18th-level spellcaster. Its spellcasting ability is wisdom (spell save DC 17, +9 to hit with spell attacks). 

Cantrips (at will): chill touch, Eldritch Blast, Mage hand, Mending, Ray of frost

1st level (4 slots): Detect magic, Identify, Alarm, Magic missile

2nd level (3 slots): Darkness, Mirror image, Flaming Sphere

3rd level (3 slots): Counterspell, Fly, Lightning bolt

4th level (3 slots): Banishment, Fire shield, Dominate Beast

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): Chromatic Wall

Multiattack. The construct can make 2 adamite double axe attacks, 1 fist attack, and 1 force ray or stomping charge attack.

Fist. Melee Weapon Attack: +10 to hit, reach 15 ft., 1 target. Hit: 16 (3d10) force damage plus 16 (3d10) bludgeoning damage.

Adamite Double Axe. Melee Weapon Attack: +9 to hit, reach 30 ft., 1 target. Hit: 32 (3d20 + 7) force damage ignoring resistance or immunity and the construct can use its bonus action to make another attack that does 13 (2d12 + 3) slashing damage and 4 (1d8) force damage. 

Force Ray. The construct blasts a powerful wave of force in a 30 ft. cone each creature in it must make a DC 22 strength saving throw or take 21 (4d12) force damage and be knocked prone.

Stomping Charge (Recharge 4-6). The construct marches up to its speed in a straight  line and it can enter another creatures space while it is marching, if the construct enters a creatures zone it must make a DC 20 dexterity saving throw or take 31 (6d12) force damage and be knocked prone.

The construct 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 construct regains spent legendary actions at the start of its turn.

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

Spiral Strike. The construct makes 1 fist attack against every creature of its choice within reach.

Smite (Costs 2 Actions). The construct makes 1 axe attack but the axe attack does an extra 11 (2d10) radiant damage and the target must make a DC 21 wisdom saving throw or become frightened until the end of the constructs next turn.

Army of Adamite (Costs 3 Actions). The construct summons up to 5 Adamite defenders but for every defender it summons it loses 10 hit points and it can only have 5 summoned at a time.