Zombie Hallwinter

Undead Steed: The undead knight rides a zombie griffin into battle using its speed to pick up enemies and drop them from up high, also uses the griffins high speed to rush back to his master to take a hit for him. For the griffin use the regular stat block add 20 HP and give undead fortitude. The griffin and Hallwinter share their turn both acting separately from each other 

Multiattack: The knight can twice attack and also throw its bola

Longsword:  Melee weapon attack +6 to hit dealing (1d8+3) slashing damage to one target

Bola: Target must make a DC 13 DEX save of be incapacitated for a turn when incapacitated roll with disadvantage when being grappled

Sworn Defender: The knight can use its mount movement to take a hit that was meant for its master using the AC of the knight