Versatile. The Dark Knight has a variety of weapons at his disposal. He has a long sword and shield, a greatsword, and a halberd. He can swap between these weapons as a bonus action. While the shield is out the Knight gains 2 AC
Multiattack. The Black Knight can make 3 Longsword attacks, 2 greatsword attacks, or 2 halberd attacks.
Longsword. Melee Weapon Attack: +9 to hit, reach 5 ft., 1 target. Hit: 9 (1d8 +5) slashing damage and 4 (1d8) radiant damage.
Greatsword. Melee Weapon Attack: +9 to hit, reach 5 ft., 1 target. Hit: 12 (2d6+5) slashing damage and 4 (1d8) radiant damage.
Halberd. Melee Weapon Attack: +9 to hit, reach 10 ft., 1 target. Hit: 9 (1d10+5) slashing damage and 4 (1d8) radiant damage.
Parry. When the Black Knight is hit by a melee attack, he can make a Strength (Athletics) check against the attack roll. if the Strength (Athletics) check is higher than the attack roll, he takes no damage and can immediately make an attack against the attacker which would count as a critical hit.