Cavalier Knight

Challenge. Once on each of the cavalier's turns when it hits a creature with a melee weapon attack, it can challenge that creature. The target must succeed on a DC 15 Charisma saving throw or else the cavalier marks it until the end of the cavalier's next turn. A marked creature that is within the cavalier's reach has disadvantage on attacks made against any target other than the cavalier. Creatures that can't be frightened are immune to this effect.

Trained Rider.  While the cavalier is mounted, it has advantage on melee attack rolls against unmounted creatures that are smaller than its mount.  It also rolls at advantage on ability checks made to ride or control its mount.  If a cavalier is charging passed a target and successfully hits the target, that target rolls with disadvantage in an attempt to take an opportunity attack on the passing cavalier and its mount.

Armored Mount.  Any mount rode by a cavalier will have leather barding, increasing its armor class by 3.  While charging a target, its armor class receives an additional 2 to its armor class.

Multiattack. The cavalier two attacks with a longsword if engaged with a target.  If the cavalier is charging upon a target, it will only make one attack with its lance or longsword.

Longsword. Melee Attack Roll: +7, reach 5 ft. Hit: 9 (1d8 + 5) Slashing damage.  If the attack is made at a charge, an additional (2d12) slashing damage is added to the attack.

Lance.  Melee Attack Roll: +8, range 10 ft. Hit: 14 (2d10+4) Piercing damage.  If the cavalier has moved 15 feet in a straight line before making this attack, while mounted, the target must make a DC 17 Strength saving throw or be knocked prone by the successful attack.  If the cavalier is mounted and the target is not mounted and is smaller than the cavalier's mount, the target rolls this saving throw at disadvantage.  

Parry. Trigger: The cavalier is hit by a melee attack roll while holding a weapon. Response: The cavalier adds 2 to its AC against that attack, possibly causing it to miss.