Iron Chariot

You are strength. You are power. You are the unstoppable force and the immovable object. You are an Iron Chariot. These knights have practiced with lance and shield to be invincible protectors of the realm, charging entire armies unscathed. 

Cavalry of One

If you have a strength score of 15 or more, you can remove the special property from the lance weapon, and can wield a shield with a lance, but no other weapons.

In addition, if you are wielding a lance, spear, trident, pike, or glaive and you run 10ft or more in a straight line before making and attack, you can add 1d6 piercing damage to the attack. This die changes to a d8 at 5th level, a d10 at 9th level, and a d12 at 13th. 

Impregnable defenses

Starting when you reach 7th level in this class, you can use your reaction to add your Constitution modifIer to your AC until the end of your next turn. 

You can use this ability a number of times equal to your proficiency bonus

Conditioning

Starting when you reach 10th level in this class, you strike with more force and are able to spot weak points easier and take people by surprise. When you use your Cavalry of One feature, you have advantage on the attack roll. 

In addition, your defenses have improved to the point where you are able to better protect those around you. Whenever someone within 5ft of you is hit by an attack roll of any kind, you can use your reaction to impose disadvantage on the attack roll. When you do so you may choose to also expend a use of Impregnable Defense to add your Constitution modifier to this creatures armor class until the end of your next turn. 

Sidesweep of Steel

When you reach 15th level in this class, you gain the ability to trip your enemies. Whenever you take the attack action with a weapon applicable to Cavalry of One, you may replace two of your attacks with a Sidesweep of Steel. Pick an Enemy within your range, and a direction you are sweeping in (clockwise or counterclockwise), you sweep your weapon at their legs, making a Strength (Athletics) check to knock the enemy prone, with a contesting Strength (Athletics) or Dexterity (Acrobatics check). If you succeed you may move to sweep the next enemy in the direction you chose, using your initial Strength (Athletics) check for each creature. Your sweep stops when you have attempted to sweep all creatures within a 10 ft arc of the original creature in the direction you chose that are in your range. You can use this feature a number of times equal to your Constitution modifier.

If you ever end your attack action with all adjacent enemies prone for any reason, you can make an additional weapon attack with your bonus action. 

Unstoppable and Immovable

Starting when you reach 18th level in this class, you gain advantage on Constitution checks, as well as Strength and Constitution saving throws, including Death saves. 

If you reach 3 successes on your Death Saves, you can roll up to half the hit dice you have left, adding your Constitution modifier for each, and arise with the number of hit points rolled. You can use this feature once per long rest, but if you use it without having any hit dice left, you only regain hit points equal to your Constitution modifier. 1 minute after using this feature you receive a level of exhaustion, and a level of exhaustion for every two hit dice you use.