Warforged Destroyer

Arcane devastators. The warforged Destroyer has two Arcane cannons built into its chassis where there would normally be a platform. The warforged Destroyer can use these cannons to unleash a devastating volley covering a wide area ahead of it or to fire at selected targets. 

Siege Monster. The warforged Destroyer deals double damage to objects and structures.

Legendary Resistance (3/Day). If Royce fails a saving throw, he can choose to succeed instead.

Overdrive (2/day). Royce internally activates his powersource, enabling him to take an additional action on his turn.

Multiattack. The warforged Destroyer makes one axehand attack and one hammerfist attack, or it fires its four shouldermounted cannons.

Axehand. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 19 (3d8 + 6) slashing damage, plus 11 (2d10) slashing damage if the target is prone.

Arcane Cannon. Ranged attack: +5 to hit, range 60ft, one target. Hit: 16 (4d8)

Hammerfist. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 19 (3d8 + 6) bludgeoning damage. If the target is a creature, it must succeed on a DC 17 Strength saving throw or be knocked prone.

Seeker Mines. (Recharge 6). The Warforged Destroyer deploys 2d4 seeker mines. The mines target anyone the destroyer can see, and the target must succeed on a DC 17 Dexterity saving throw, or take (1d4) force damage for each mine targeting them. 

Arcane Volley (Recharge 6). The warforged Destroyer unleashes a barrage of arcane bolts from the cannons on its shoulders, and each creature in a 30ft cube in front of it must make a DC 17 Dexterity saving throw. A creature takes (10d8) force damage on a failed save, or half as much damage on a successful one.

Emergency forcefield (1/day). If Royce's HP goes below 10% of his max, a forcefield activates and surrounds him. The forcefield has the same effects as the Resilient sphere spell. This ability resets after a long rest.