Actions

Multiattack The Knight can make three attacks listed below.
Stunning Stamp Creatures within a 10 ft. cone must succeed a Dexterity Saving Throw (DC = 15), or be Knocked Prone and take 1d6 bludgeoning damage.
Magic Ore Longsword Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 1d8+6 slashing damage when attacked with one hand or 1d10+6 when wielded with two.

Reactions

Riposte Shield Bash If the Knight successfully blocks a melee attack, he can use his Reaction to make a Goring Bash. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 1d10+4 bludgeoning + 1d4 piercing damage. The creature must succeed a Strength Saving Throw (DC = 14) or be knocked Prone.

Legendary Actions

Upon reaching half HP, the Knight gets one Legendary Action per turn, which can be used for the following:   Radiant Skysweep (Recharge 5-6): The knight flies in a 20x5 ft. line. Each creature in that line must succeed a DC 16 Dexterity Saving Throw or take 4d8+6 piercing damage. Radiant Tail: All creatures within 15 ft. of the Knight must succeed a Dexterity Saving Throw DC 14, or take 3d6+4 slashing damage. If the Knight was hit by three or more attacks prior to this action, the range extends by 30 ft.