Warforged Colossus 1.0

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

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

Siege Monster. The colossus deals double damage to objects and structures.

Towering Terror. Any enemy outside the colossus that starts its turn within 30 feet of it must succeed on a DC 26 Wisdom saving throw or be frightened until the start of the enemy’s next turn. If the enemy’s saving throw is successful, it is immune to this colossus’s Towering Terror for the next 24 hours.

Multiattack. The colossus makes three attacks — one with its arcane chain sword and two with its eldritch cannons — then uses it's Dragon's Breath Cannon.

Arcane Chain Sword. Melee Weapon Attack: +18 to hit, reach 20 ft., one target. Hit: 29 (3d12 + 10) magical piercing and slashing damage, and the colossus can push the target up to 20 feet away from it.

Eldritch Cannon. Ranged weapon Attack: +18 to hit, range 300 ft., one target. Hit: 18 (4d8) magical piercing damage, and if the target is a large or smaller creature, it is knocked prone.

Dragon's Breath Cannon.  The Colossus aim's its arm cannon and releases a 60 foot cone of elemental energy chosen when the attack is made. (Fire, Lightning, Acid, Poison, or Cold). Creatures in the area have to make a DC 20 dexterity saving throw, or take 8d8 of the chosen damage, or half on a successful save.

 Incinerating Beam (Recharge 5–6). The colossus fires a beam of light in a 150-foot line that is 10 feet wide. Each creature in the line must make a DC 20 Dexterity saving throw, taking 60 (11d10) radiant damage on a failed save, or half as much damage on a successful one. A creature reduced to 0 hit points by this beam is disintegrated, leaving behind anything it was wearing or carrying.

Arcane Vulcan Cannon. (Recharge 5-6) The colossus's arm cannon shifts into a vulcan cannon and unleashes a torrent of enchanted bullets. Creatures in a 60 foot cone in front of the colossus then make a DC 20 Dexterity saving throw. Roll 1d20+3, then use that to determine how many 1d6 dice you roll for damage (magical piercing). On a failed save, creatures will take full damage, and half on a success.

Arcane Shield. (5 per long rest) As a reaction, the colossus can activate an arcane shield, granting it a +5 to it's AC until the start of its next turn.