Warp Crystal Golem

Energy Absorption. Whenever the golem is subjected to fire, lightning, thunder, or force damage, it takes no damage and instead regains a first-level spell slot for each 15 damage it takes. For each 10 damage above that, it regains a spell slot of a higher level, this can continue for spell slots up to 9th.

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

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

Magic Weapons. The golem's weapon attacks are magical.

Spellcasting. The Golem is a 10th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 15, +7to hit with spell attacks). It has the following spells prepared:

1st level (3 slots): Magic Missile, Thunderwave,  Absorb Elements

2nd level (2 slots): Shatter

3rd level (2 slots): Lighting Bolt

4th level (1 slot): Wall of Fire

5th level (1 slot): Antilife Field

Multiattack. The golem makes two melee attacks.

Crush. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 20 (3d8 + 7) bludgeoning damage.

Slam. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:11 (1d12 + 5) bludgeoning damage. If the target is large or smaller, it is pushed back10 ft and knocked prone.