Wyvern-mounted knights of superior skill, Wyvern Lords are units that stand out for not just high movement, but also the ability to traverse terrain that is normally impassable. Wyvern Lords typically excel in strength, stamina, and defense, and thus make for fairly decent combatants against regular enemy units.

Wyvern Companion

At 3rd level, you gain a wyvern companion that accompanies you on your adventures and is trained to fight alongside you. Its hit point maximum equals the hit point number in its stat block. Like any creature, it can spend Hit Dice during a short rest to regain hit points.

The wyvern obeys your commands as best as it can. It takes its turn on your initiative. On your turn, you can verbally command the wyvern where to move (no action required by you). You can use your action to verbally command it to take the Attack, Dash, Disengage, or Help action. If you don't issue a command, the wyvern takes the Dodge action. If you are incapacitated or absent, the wyvern acts on its own, focusing on protecting you and itself. The wyvern never requires your command to use its reaction, such as when making an opportunity attack.

You have advantage on saving throws made to avoid falling off your wyvern. If you fall off your wyvern and descend no more than 10 feet, you can land on your feet if you’re not incapacitated. 

If the wyvern dies, you can obtain a new companion by spending 24 hours bonding with a wyvern that isn’t hostile to you and that meets the requirements, or you can spend 3000 gp to purchase and outfit a replacement.

Trample

Starting at 3rd level, your aerial superiority causes your foes to buckle under pressure. When your wyvern lands an attack against another creature while you are riding it, you can use your bonus action to force the target to make a Constitution saving throw (DC = 8 + your Strength modifier + your proficiency bonus). On a failed save, the target takes an additional 1d4 bludgeoning damage and is knocked prone. You cannot use this feature if the target is already prone or is incapacitated.

You have one use of this ability, and you regain all expended uses of it when you finish a long rest. You gain an additional use when you reach 7th, 10th, 15th, and 18th level. The amount of damage taken also increases at certain levels: 1d6 at 7th level, 1d8 at 10th level, 1d10 at 15th level, and 1d12 at 18th level.

Lunge

At 7th level, even the nimblest of enemies are unable to escape you. When you can use your reaction to make an opportunity attack against a creature, you can ignore all abilities that would normally avoid opportunity attacks. 

Quick Burn

At 10th level, you experience a rush of adrenaline at the dawn of battle. When you make an attack roll against a creature, you can use this feature to add a bonus equal to your Strength modifier (min of 1). Additionally, when a creature you can see makes an attack roll against you, you can use your reaction to increase your AC by your Strength modifier (min of 1). The amount you can increase your attack roll or your AC decreases by one for each turn you take in the combat.

Once you use these features, you cannot use them again until you finish a long rest.

Light Weapon Breaker

At 15th level, you can turn an opponent's strength into their weakness. Any attack rolls made against you with a weapon that has the Light property are made with disadvantage. Additionally, any attack rolls you make against a creature wielding a weapon with the Light property are made with advantage.

Savage Blow

At 18th level, the ferocity of your strikes can be felt across the battlefield. When you land a critical hit against a creature, you can use this feature to force all creatures within 15 feet of you to make a Constitution saving throw (DC = 8 + your Strength modifier + your proficiency bonus). On a failed save, the creature takes half of the damage you rolled (rounded down).

Once you use this feature, you cannot use it again until you finish a long rest.