After striking your foe, you twist the blade.

When you hit a creature with a melee weapon attack on a roll of 18 or 19, you can use your reaction to turn the attack into a critical hit.

Withdrawing into your mind, you focus and concentrate to steel your nerves.

Deftly surging forward and weaving around your opponent, when their attack fails you quickly move around your foe and force them to stumble.

You offer inspiring encouragement to an ally and they gain their second wind.

When an ally you can see takes damage from an attack, you can use your reaction to release a hearty rallying cry. As long as they are able to hear you, your ally regains an amount of hit points equal to twice your proficiency bonus.

You interpose yourself to take a hit for your ally.

When an ally within your reach is hit by an attack, you can use your reaction to swap places with them and become the target of that attack, taking half as much damage as normal.

As your ally strikes an opponent, you seize the moment of imbalance to knock them down.

Watching a companion under attack infuriates you and you fling yourself at their opponent with a powerful shove.

After a creature within your reach makes a melee attack against an ally, you can use your reaction to make an Athletics check against the creature’s maneuver DC. On a success you shove the creature 10 feet away from you and you move 10 feet in that direction. 

Your mount takes comfort from your presence and gains its second wind.

When your mount is hit by an attack, you can use your reaction to pat it reassuringly. Your mount regains hit points equal to your level. 

Your mount makes an incredible leap, soaring through the air.

When your mount makes an Athletics check to jump, you can use your reaction to grant it a fly speed equal to half its Speed until the end of your turn. Your mount can only fly in a straight line.

Under fire, you dive for cover.

When you are targeted by a ranged attack, after it hits or misses you, you can use your reaction to move up to your Speed. 

If your movement ends adjacent to either a solid barrier as big as you are or a creature the same size as you or larger, until the beginning of your next turn you have three-quarters cover against ranged attacks (+5 bonus to AC and saving throws) as long as you remain adjacent to the barrier or creature.