Blood Dragon Oil

Legendary Resistance (3/Day, or 4/Day in Lair). If the blood dragon oil fails a saving throw, it can choose to succeed instead.

The Factory: the chest of the blood oil dragon is hollowed out and was replaced with heavy infernal looking machines with spinning wheels, cogs and metal chains in the middle of the chest there its heart and as long that no one destroy it - he will never die and regenerate 10 heat point every turn. you cannot destroy the heart from outside the Dragon body. To destroy the heart you need to go next the dragon, sacred in DC 18 dex saving throw [sow you will not get grabbed by the chains ] and at the next turn go inside the dragon chest and have the same save with disadvantage to rich the heart - only then, on the therd turn one can attack and destroy the beating heart that have armor 14 and 40 HP

Multiattack. The dragon makes three Rend attacks. It can replace one attack with a use of Spellcasting to cast Shatter.

Rend. Melee Attack Roll: +12, reach 10 ft. Hit: 16 (2d8 + 7) Slashing damage plus 5 (1d10) Fire damage as the Blood Dragon Oil sprey you with burning oil as he attack. 
The target of the attack need to save strength DC 18 or to be pushed 15 Feet away from the dragon and get 10 (2d10) bludgeoning damage. 

Hot Tarr Breath (Recharge 5–6). Dexterity Saving Throw: DC 19, each creature in a 90-foot-long, 5-foot-wide Line. Failure: 60 (11d10) fire damage. Success: Half damage. 
One who failed the saving throw have the burning condition and get 8 (2d8 ) fire damage at the start of his turn from the Tar that cover them until they spend an action to clean themself or an ally help them to do this.
In adition the Hot Tarr Breath leve a 30 foot cone of hot tar that act as a difficult terrain. 

Chains of Doom: Each round the dragon can send on chain up to 60 feet from its chest toward an enemy that need to have a dexterity save DC 18 or to be grappled and restrained . the blood oil dragon can chain up to 4 large or smaller individuals with different chains at a time, people grapeld in this way don't hinders its movement.

Every round a target is still grappled he is pulled 15 feet towerd the dragon, sufer Melee Attack Roll: +12, reach 10 ft. Hit: 16 (2d8 + 7) Slashing damage plus need to have a Constitution save DC 18 or have a limb incerted with metal shards and spikes, its have only cosmetic afect but it can be held only with the spells]heal[/spells] spell or spells]greater rasterization[/spells].

Colector of flesh  when an unconscious person drops to 0 hit points 30 feet of the dragon he can use his reaction to send a chain that will drag the body into The Factory. If the person die there he will spawn as a machine zomby after one round

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature’s turn, the dragon can expend a use to take one of the following actions. The dragon regains all expended uses at the start of each of its turns.

Cloaked Flight. The dragon uses Spellcasting to cast Invisibility on itself, and it can fly up to half its Fly Speed. The dragon can’t take this action again until the start of its next turn.

Sonic Boom. The dragon uses Spellcasting to cast Shatter. The dragon can’t take this action again until the start of its next turn.

Tail Swipe. The dragon makes one Rend attack.