Runic Colossus

The colossus is immune to any spell or effect that would alter its form.

The colossus has advantage on saving throws against spells and other magical effects.

The colossus deals double damage to objects and structures.

The colossus makes two Slam attacks and then uses Stomp.

Melee Attack Roll: +14 to hit, reach 20 ft., one target. Hit: 26 (3d12 + 7) bludgeoning damage.

Melee Attack Roll: +14 to hit, reach 20 ft., one target. Hit: 29 (4d10 + 7) bludgeoning damage. If the target is a Huge or smaller creature, it must succeed on a DC 22 Dexterity saving throw or have the prone condition. Until the colossus uses its Stomp again or moves, the creature has the restrained condition. The restrained creature or another creature within 5 feet of it can use its action to make a DC 22 Strength check. On a successful check, the affected creature relocates to an unoccupied space of its choice within 5 feet of the colossus and is no longer restrained.

The colossus fires a beam of magical force from its chest, hands, or head in a 150-foot line that is 10 feet wide. Each creature in that area must make a DC 22 Dexterity saving throw, taking 58 (9d12) force damage on a failed save, or half as much damage on a successful one.

Ranged Spell Attack Roll: +14 to hit, range 120 ft., one creature casting a spell of 5th level or lower. Hit: 26 (4d12) force damage, and the target must succeed on a DC 15 Intelligence saving throw or the spell fails and has no effect.