The Counterist

Level 3: The Duelist's Advance

3rd-level Counterist feature
You have mastered the art of the combat posture, allowing you to shift your center of gravity and intent to suit the flow of battle. You enter combat in a neutral stance. Your stance changes automatically based on the actions you take:

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  Aggressive Stance. You enter this stance immediately after taking the Attack action on your turn. In this state, your movements are forward-pressing and intimidating, designed to break the enemy's guard.
• Defensive Stance. You enter this stance immediately after taking the Dodge action on your turn, or after using your Cunning Action to take the Dodge action. In this state, you are a coiled spring, absorbing the enemy's momentum to find a gap in their armor. Your stance lasts until the start of your next turn, or until you are incapacitated.

Level 3: Ruthless Instruction

Codigra

When a creature misses you with a melee attack while in your Defensive Stance, you can trap their weapon or limb. You can use your reaction to force the creature to make a Strength saving throw against your Maneuver DC. On a failed save, the creature is knocked prone and its speed becomes 0 until the start of its next turn.

Flèche

When a creature hits you with a melee attack while in your Defensive Stance, you can lean into the blow to minimize damage and snap back with a strike. You can use your reaction to reduce the damage by 1d10 + your Dexterity modifier + your rogue level. If you reduce the damage to 0, you can immediately make one melee weapon attack against the attacker as part of the same reaction.

Goadation

As a bonus action while in your Aggressive Stance, you can hurl a vicious, mocking challenge at a creature within 30 feet of you that can hear you. The target must succeed on a Wisdom saving throw against your Maneuver DC. On a failed save, the target is provoked into a blind rage, granting it disadvantage on all attack rolls against targets other than you until the start of your next turn.

Killing Intent

When you deal damage to a target while in your Aggressive Stance, you leave them shaken and off-balance. The target suffers disadvantage on the next attack roll it makes before the start of your next turn.

Kyo-Jitsu

When you take the Attack action while in your Aggressive Stance, you can forego one of your attacks to execute a deceptive movement. Force a creature within 10 feet of you to make a Wisdom (Insight) check against your Maneuver DC. On a failure, your next attack against that target before the end of your turn has advantage and ignores half and three-quarters cover.

Mu-Shin

When you hit a creature with a melee weapon attack while in your Aggressive Stance, you can strike the weapon from their grip. Force the target to make a Strength saving throw against your Maneuver DC. On a failed save, the creature drops one item it is holding of your choice, which lands up to 10 feet away from it.

Pocket Sand

When a creature within 10 feet of you declares an attack against you while in your Defensive Stance, you can use your reaction to throw a handful of grit, ash, or debris into its eyes. The attacker must make a Constitution saving throw against your Maneuver DC. On a failed save, the creature is blinded until the start of its next turn, causing the triggering attack (and any subsequent attacks made before its next turn) to be made with disadvantage.

Quinggong

When a creature targets you with a melee attack while in your Defensive Stance, you can use your reaction to leap out of harm's way. You move up to 15 feet away from the attacker without provoking opportunity attacks. If this movement takes you out of the attacker's reach, the attack automatically misses.

Shi Long Wu

While in your Defensive Stance, you can draw the enemy's focus away from your allies. When an enemy within 30 feet of you targets an ally with an attack, you can use your reaction to force the attacker to make a Wisdom saving throw against your Maneuver DC. On a failed save, the attacker must target you instead, provided you are within its reach or range.

The Boot

When you hit a creature with a melee attack while in your Aggressive Stance, you can force the target up to 10 feet directly away from you, or move up to 10 feet toward it without provoking opportunity attacks, provided the target is Large or smaller. 

Zanshin

When an attack misses you while in your Defensive Stance, you use the momentum of the miss to reposition. You can use your reaction to move up to half your speed without provoking opportunity attacks.

Level 9: Relentless Tempo

9th-level Counterist feature
Your mastery of the rhythmic flow of combat allows you to extract more power from your stances.

• Aggressive Flow. While in your Aggressive Stance, your strikes carry overwhelming momentum. Once per turn when you deal weapon damage to a creature, you deal an additional [roll]1d6[/roll] damage of the weapon's type.
• Defensive Flow. While in your Defensive Stance, you are so attuned to the enemy's movements that you no longer need to deliberate on your counters. You can make opportunity attacks without expending your reaction, up to a number of times per round equal to your proficiency bonus.
  
  Additionally, when you hit a creature with your Opportunistic Riposte, you add your proficiency bonus to the damage roll, and the target's speed is reduced to 0 until the end of its current turn.

Level 13: Mortal Opening

13th-level Counterist feature
You have learned to strike not just the body, but the enemy's very will to fight. When you deal damage to a creature using a reaction granted by this subclass, you hit a vital nerve or break their posture. The target must succeed on a Constitution saving throw against your Maneuver DC or become stunned until the end of its next turn. Once a creature succeeds on this saving throw, it is immune to this effect for 24 hours.

Level 17: To The Death

17th-level Counterist feature
You have reached the pinnacle of the duelist's art, turning the transition between stances into a lethal weapon.

• The Lethal Shift. When you transition from your Defensive Stance to your Aggressive Stance, you strike with perfect precision. Your first melee attack on that turn is automatically a critical hit.
• The Unattainable Mark. When you transition from your Aggressive Stance to your Defensive Stance, you become an enigma in motion. Incoming attack rolls against you suffer a penalty equal to your Dexterity modifier until the start of your next turn.