You react and attack quicker than the eye can see.

After rolling initiative, you can use your reaction to treat your initiative as if you had rolled a critical success.

You dart forward and snatch an item from a foe just as they start to use it.

You swiftly adjust your enemy’s armor so that they cannot move.

You redirect your enemy’s attack back upon itself.

With a vicious strike, you

You nearly lose

All your training culminates in this lethal attack. You deliver the perfect killing blow with a single secret technique.

You tune your senses, focusing on the fight at hand.

You and your allies combine forces and attack a single foe with devastating results.

Make a melee weapon attack against a creature. Any willing ally within your reach can use their reaction to make a melee weapon attack against the same creature. 

If the creature is hit by two attacks, it takes extra damage equal to your proficiency bonus. 

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.