Blood Plate

Bloody Plate. When Blood Plate is below half of his maximum HP, his armor class is reduced to 14.

Mendable. Blood Plate can be targeted by mending, and regains 1d4+(caster's spellcasting ability modifier) HP from the spell.

Whirling Blade. When Blood Plate deals damage with a melee weapon attack, he may use his bonus action to attack a different target within range immediately after.

Infest. When Blood Plate deals damage to another creature, they must make a DC 13 Constitution saving throw. On a failure, the creature takes an additional 5 (2d4) poison damage, and another 5 (2d4) poison damage at the beginning of Blood Plate's next turn. 

Legendary Resistance (3/Day). When Blood Plate fails a saving throw, he can choose to succeed instead.

Multiattack. Blood Plate makes two attacks, both with his Hellstroke Axe.

Hellstroke Axe. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit:  18 (3d6 + 8) slashing damage. 

Repeating Hellfire Crossbow. Ranged Weapon Attack: +7 to hit, range 60/120 ft., one target. Hit: 10 (2d6 + 3) piercing damage.

Blood Plate can take up to 2 legendary actions per round.

Attack (Costs 1 Action). Blood Plate takes the Attack action. This cannot trigger Whirling Blade.