Axiom Colossus

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

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

Siege Engine. The Axiom Colossus deals double damage to objects and structures.

Axiomatic Core. At the start of each of its turns, the colossus chooses one creature it can see within 60 feet. Until the start of its next turn, that creature cannot benefit from advantage on attack rolls or saving throws.

Multiattack. The Axiom Colossus makes three attacks.

Adamantine Fist. Melee Weapon Attack: +15 to hit, reach 15 ft., one target.
Hit: 29 (4d10 + 9) bludgeoning damage.

Gravitic Slam (Recharge 5–6). The colossus smashes the ground. Each creature on the ground within 20 feet must make a DC 20 Strength saving throw or take 45 (7d12) bludgeoning damage and be knocked prone. On a success, a creature takes half damage and isn’t knocked prone.

Annihilation Beam (Recharge 6). The colossus fires a focused beam of ordered force in a 120-foot line that is 10 feet wide. Each creature in the line must make a DC 20 Dexterity saving throw, taking 72 (16d8) force damage on a failed save, or half as much on a successful one.

Objects in the line automatically fail the save.

The Axiom Colossus 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.

Move. The colossus moves up to half its speed.

Strike. The colossus makes one Adamantine Fist attack.

Suppress Magic (Costs 2 Actions). Until the end of the colossus’s next turn, spells of 5th level or lower cast within 20 feet automatically fail unless cast with a successful DC 18 spellcasting ability check.