Excal-heim
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.
Siege Monster. The golem deals double damage to objects and structures.
1/10 chance to drop the Tome of the Void.
Multiattack. The golem makes two slam attacks. Slam. Melee Weapon Attack: +12 to hit, reach 5 ft, one target. Hit: 23 3d10+7 bludgeoning damage.
Impact (Recharge 3-4). When is hit by a spell, it can launch itself 15-feet up and up to 60-feet towards the caster, performing a Slam attack upon landing. On a hit, the target becomes stunned until the start of the golem's next turn in addition to the damage dealt.