Calvary Unit (Centaur Only)

Same Centaurs can operate as mounts, you are one.

Born with a Saddle

Starting at level 3, Your ability to act as a mount becomes apparent. You're treated as large for any prepossess that would involve being a mount.
When you equip Pole-arm(s) you can do so as a one-handed weapon, and you no longer get disadvantage on attacks with lances when within 5 feet of your target.
Finally you can allow someone to use only 5 feet of there movement to mount or dismount you.

Reaction Attack

Starting at 3rd level, When mounted and your rider makes a weapon or spell attack at an enemy that is within your weapon range, You can use your reaction to make one attack against that same target.
Finally if the target had an Unwavering Mark on it from the (Fighter)Cavalier Class the attack deals extra damage equal to 1/2 your fighter level.

Warding Maneuver

At level 7, You learn how to fend off strikes directed to You're self, Your Rider or any other creature nearby.
If you or a creature within 5 feet of you is hit by an attack, you can as a Reaction to roll 1d8 as a reaction and add the number rolled to there AC for that attack. If the attack still hits, the target has resistance to that attacks damage, You must by wielding a melee weapon or shield to use this ability.
You can use this ability a number of time equal to your construction modifier (minimum of once), and you regain all uses of this ability after a long rest.

Crashing the Line

At 10th level, You became a master of limiting your enemy's movement. Creatures provoked opportunity attacks from you when moving 5 feet or more when within your reach, if you hit a creature with an opportunity attack its speed is reduced to 0.
Finally if you used your hooves for the reaction attack, the target must make a Strength saving throw (DC 8 + proficiency + Strength modifier) or be knocked prone.

Pegasus Wings

Beginning at 15th level, You grow a set of Pegasus Wings granting you a fly speed equal to twice your base movement speed as long as your not encumbered.
(NOTE: encumbered is based on the total combined weight of Your Gear + Your Riders Gear , and the Rider them self.)

Vigilante Defender

Starting at level 18, You respond to danger with extreme vigilance. In combat, you gain a special reaction that you can use once on every turn except your own, you can only use this reaction to make a reaction attack except on the turn you use your own reaction.