Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Metal Body: This dragon is resistant or immune to most types of damage thanks to its metal body not much is effective against this dragon. This dragon's body constantly is rotating and moving to make it very hard to hit as well as causing 3d12 + 4 slashing damage to all those within 10ft of this dragon. This dragon's spikes move at high speed.

Shredding Bite: Every time a target is hit by this dragon you must make a DC 18 CON saving throw or have tiny microscopic sawblades be put into your body dealing 2d8 + 5 slashing damage this includes every attack the dragon can make. This damage happens once per turn. To get rid of the saw blades you make a DC 17 Con - 1 for every turn that is passed you can make this save at the beginning of every turn. 

Lighting Rod: This Dragon is empowered by a lighting damage-based attack giving an extra 1d12 to hit and 1d20 to all its damage rolls if it was hit by lightning or thunder damage on its last turn or targeted by that type of damage on its last turn. 

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +17 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 10) piercing damage plus 14 (4d6) fire damage.

Claw. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 17 (2d6 + 10) slashing damage.

Tail. Melee Weapon Attack: +17 to hit, reach 20 ft., one target. Hit: 19 (2d8 + 10) bludgeoning damage.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 21 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

Metal Shard Breath (Recharge 10). The Dragon exhales in 60ft cone launching a hail of metal shards infused with all sorts of chaotic metal energy dealing 100 (9d20 + 10) slashing damage to all those hits if the save is made half of this damage the DC for this is a DC 19 CON. The area in which this breath was used inlays the ground in sharp shards of metal making the terrain difficult the dragon can freely use these metal shards on the ground using a Bonus action to form the metal shards into fully form spikes about 5 feet in length and about 2 feet in diameter. About 5 of these spikes can be created per breath weapon use. 

Impaling force: This dragon can use this action when there are metal spikes formed on the ground launching them at a target each spike can impale up to two people at once if those two people are in a line. This spike deals 6d12 + 5 piercing damage to all those that are impaled by it. The DC to not be impaled is DC 18 DEX saving throw if you are hit you can make a DC 19 CON saving throw to take half damage. 

Metal Scream: The Dragon yells out in a massive area covering 200ft of range all those in this area must make a DC 16 WIS saving or have your eardrums bleed dealing 3d20 force damage and you are deafened until you are healed to max hp. It can only do this once every 6 turns. 

Shredding: as a reaction, the dragon can negate your attack if your weapon is made of any kind of metal manipulating it took attack you instead of the dragon taking the attack rolls and damage rolls instead target you. Other weapons effects do not activate on you only the weapon damage itself.  This effect does not affect magical weapons or enchanted weapons. It can affect ranged weapons as well. 

The dragon 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. The dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 15 feet of the dragon must succeed on a DC 25 Dexterity saving throw or take 17 (2d6 + 10) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.