Ancient Golem

Fire and Cold Absorption. Whenever the golem is subjected to fire or cold damage, it takes no damage and instead regains a number of hit points equal to the fire or cold damage dealt.

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.

Ancient knowledge. If asked a question, it can always answer with the right answer.

Multiattack. The golem makes two melee attacks.

Giant Fist. Melee Weapon Attack: +15, reach 10 ft., one target. Hit: 30 (3d10+15) bludgeoning damage.

Stomp. Melee Weapon Attack: +15, reach 5 ft., one target. Hit: 33 (3d12+15) bludgeoning damage. 

Giant Warhammer. Melee Weapon Attack: +15, reach 5ft., one target. Hit: 46 (6d12+10) bludgeoning damage.

Power of the Plane (5/day). Ranged Weapon Attack: +3, reach 100ft., 1d4 targets. Hit:  Targets have to make a DC 15 wisdom saving throw or take 84 (14d12) force damage on a fail or half on a succes. (only usable by Ace-giants)

Detect. The golem makes a Wisdom (Perception) check, with advantage.

Spell Knowledge. The golem can mimic any spell used against it in its turn after the spell has been used on it.

Hard Body (5/day). On its turn the golem can use this action and harden its body, making it so it has resistances to any attack.