Arcanite Blackhammer

Siege Walker. The Blackhammer deals double damage to objects and structures. Objects with resistance to damage done by the Blackhammer still take full damage, and objects with immunity take half damage.

Magic Resistance. The Blackhammer has advantage on saving throws against magic and magical effects.

Hardened Shields. The Blackhammer gains 12 temporary hitpoints at the start of each of its turns while it has at least 1 hitpoint. While it has these hitpoints, the Blackhammer takes 3 less damage from all sources that aren't adamantine. This reduction is increased to 6 for damage from spells or other magical effects that do not involve a weapon attack from an adamantine weapon.

Constructed Nature. The Blackhammer does not require food, air, or rest. It cannot regain hitpoints naturally, nor can it benefit from healing magic. The Blackhammer may regain hitpoints if at least one creature who has proficiency with it spends 8 hours repairing it with Smith's tools. At the end of this period, the Blackhammer regains 3d12 + 7 + The creature's arcana bonus hitpoints, plus 3d12 for each additional creature who repaired it for this duration. A mending spell cast on the Blackhammer instantly restores 1d4 hitpoints for it, to a maximum of 50 hitpoints every 24 hours.

Top-heavy. When the Blackhammer falls prone, it takes 15 bludgeoning damage. The Blackhammer must use its action to stand up rather than costing movement. Damage taken from this effect does not benefit from the Blackhammer's Hardened Shields feature.

Trample. When the Blackhammer enters, moves through, or ends its turn in another creature or object's space, that creature or object takes 18(5d6) Bludgeoning damage. This Damage is considered to be Adamantine. Any creature that takes this damage must succeed on a DC 22 Strength saving throw or be knocked prone. A creature cannot take this damage more than once per round.

Interior. The Blackhammer has an interior that includes a cockpit and controls, a 10ft by 10ft storage room, and a small apartment including a cot, a toilet, and a small set of exercise weights. The interior can be accessed via a hatch, which can be reached using a set of ladders on the side of the mech. The hatch locks while the Blackhammer is in operation, requiring a DC 30 Strength(Athletics) check or a DC 20 Dexterity(Sleight of Hand) check to open while locked. Additionally, if the Blackhammer moves or takes an action while a creature is navigating the ladders or attempting to open the latch, the creature must succeed on a DC 16 Dexterity saving throw or be thrown from the mech, falling 30 feet.

Pilot. The Blackhammer cannot function without a pilot, and is incapacitated when it lacks one. The Blackhammer's Intelligence, Wisdom, and Charisma Scores, including any passive scores or ability bonuses, are replaced with its pilot's if its pilot's are higher than the Blackhammer's. The Blackhammer is wholly controlled by its pilot, which must use its complete attention to operate the mech. A pilot inside the Mech is behind full cover for all effects that originate outside the Blackhammer's interior, and it is considered Petrified, though it remains aware of its surroundings and retains control over the Blackhammer. A creature can only pilot the Blackhammer if it has proficiency with Colossal Mechanical Vehicles.

Multiattack. The Blackhammer makes three weapon attacks, two with its Mjolnir Cannons and one with its Helfire Missiles.

Mjolnir Cannons. Ranged Weapon Attack, +14, 1 target, 60/300. Target takes 21 (6d6) Fire damage and 21 (6d6) Thunder damage. All creatures and objects within 5 feet of the target must make a DC 16 Dexterity saving throw, taking 14 (4d6) Fire damage and 14 (4d6) Thunder damage on a failed save, or half as much on a successful one. Any creature within 10 feet of the target must succeed on a DC 16 Constitution saving throw or be deafened until the end of its next turn.

Helfire Missiles. Ranged Weapon Attack, +14, 6 targets, 120/360 ft. Target takes 7 (2d6) Fire damage and 7 (2d6) Thunder damage. All creatures and objects within 5 feet of the target must make a DC 16 Dexterity saving throw, taking 4 (1d6) Fire damage and 4 (1d6) Thunder damage on a failed save, or half as much on a successful one. Any creature within 10 feet of the target must succeed on a DC 16 Constitution saving throw or be deafened until the end of its next turn.

40mm Strike Cannon. Ranged Weapon Attack, 600/1800 ft. All creatures within a 20 ft sphere centered on a target point within range must make a DC 16 Dexterity saving throw, taking 50 (14d6+1) Fire damage and 50 (14d6+1) Thunder damage on a failed save, or half as much on a successful one. Any creature within 60 feet of the target location must succeed on a DC 16 Constitution saving throw or be blinded and deafened until the end of its next turn. This attack cannot target a point within 300 ft. of the Blackhammer. [Recharge 5-6]

Self Destruct. If the Blackhammer is below 30 hitpoints, it may use this reaction to begin a Self Destruct timer. The timer automatically ends and the Blackhammer self destructs if the Blackhammer is reduced to 0 hitpoints. When this reaction is taken, the Pilot is ejected 100 feet in the air and 200 feet to the rear of the Blackhammer. The Pilot falls harmlessly to the ground at a rate of 35 ft per round, unless the pilot takes 15 or more damage in that time, which causes them to instantly fall the remaining distance. At the start of the Blackhammer's next turn, it Self Destructs, causing all creatures within 40 ft. to make a DC 16 Dexterity Saving throw. Creatures within 10 ft. of the Blackhammer automatically fail this save. Any creatures and objects in the interior of the Blackhammer are instantly destroyed. All creatures and objects within range take 75 (21d6+1) Fire damage and 75 (21d6+1) Thunder damage, or half as much on a successful save. If this reduces a creature to 0 hitpoints, the creature instantly dies and its body is destroyed. All flammable objects in range are Incinerated, and all objects destroyed by the blast are incinerated. The Blackhammer is also destroyed, leaving behind only molten metal and charred materials.  Any creature within 200ft of the Blackhammer must succeed on a DC 21 Constitution saving throw or be blinded and deafened until the end of its next turn.

Disruption Pulse. The Blackhammer attempts to interrupt a creature in the process of casting a spell within 60 ft of itself. If the creature is casting a spell of 3rd level or lower, its spell fails and has no effect. If it is casting a spell of 4th level or higher, the Blackhammer makes a Constitution saving throw. The DC equals 10 + the spell's level. On a success, the creature's spell fails and has no effect. The Blackhammer may use this reaction 3 times, regaining all uses after 8 hours have passed without a use being expended.

The Blackhammer takes 3 legendary actions per round. The Blackhammer cannot take legendary actions if it is below 50 Hitpoints.

Missile Barrage. The Blackhammer makes 1 Helfire Missiles attack

Hammer Down (Takes 2 Actions) The Blackhammer Slams the ground with explosive force. All creatures within 30 feet of the Blackhammer that are touching the ground must succeed on a DC 22 Strength saving throw or fall prone, taking 18 (2d6+11) Bludgeoning damage. Any creature in the air must succeed on a DC 22 Dexterity saving throw or take 18 (2d6+11) Thunder damage and fall 30 feet.

Scan. The Blackhammer makes a Wisdom(Perception) check using its tremor sense with advantage.