Some prefer offense, while others prefer defense. Practitioners of the Diamond Viper style prefer to think of the two as one in the same. Opting to understand the perilous front line rather than seek to avoid it, the Diamond Viper aims to bend that front line to their will with reversals, razor sharp reflexes, and capitalizing upon the openings of vulnerability within an opponents defenses when striking at these opportune moments in-between their offense. Practitioners of the Diamond Viper have also trained their minds and bodies to withstand a remarkably higher threshold of damage than most Martial Arts through rigorous, often brutal training.

Toughness

At third level, your training has well prepared you for the rigorous physical durability required for such an up front and dangerous martial art such as this. You attain the effects of the feat Tough as a feature of this subclass.

Observational Precision

Also at third level, your reflexes and ability to read an opponents movements has been honed to razor sharp levels.

• When a creature hits you multiple times in a single turn, whether you are hit or not, you gain +1 AC for each additional hit they make on you. This only lasts for that creatures' turn.
• If you miss an attack, the next subsequent attack you make against a creature in that same turn (if available) has advantage.
• You are proficient in Perception and Sleight of Hand checks. Additionally, you may spend a Ki point to reroll checks of either and take the higher of the two rolls. You may only do this once per check.

Counterstance

At sixth level, you learn a series of postures and stances which not only make you harder to hit, but give you ample opportunity to feint an attack and counter with incredible speed. As part of your attack, you may withhold one of your two attacks from the Extra Attack feature and instead gain +2 AC for the duration. If a creature attacks you while in counterstance, and misses, you may as a reaction make an attack against that creature as long as they are in range. This attack may be either with a weapon or bare handed,and may be substituted for any attack action such as shove or grapple.

Momentum Reversal

As an additional feature of Counterstance, your ability to reverse the momentum of a fight in order to create openings of vulnerability in an opponent is honed. When you perform a counter attack from counterstance, you may spend a Ki point along with it to enhance the attack. If Stunning Strike is used with that attack, the target's Wisdom saving roll must have a 1d4 plus your Wisdom modifier substracted from it.

Grim Determination

At eleventh level, you are specially trained to channel your determination to perservere into incredible fortitude. When your HP is depleted to half of your maximum HP, you gain resistance to slashing, piercing, and bludgeoning damage.

Uninterrupted Momentum

Also at Eleventh level, you learn to capitalize on the momentum of an attack. If you manage to strike an opponent at least four times in a single full turn and you attempt a Stunning Strike on the fourth, the creature rolls the save with disadvantage.

The Diamond Viper

At seventeenth level, your defensive prowess has honed to the level of a master, allowing you to optimize counter damage and bolster your rock solid resistance with masterful use of Ki.

• Attacks made against targets that are incapacitated, blinded, or prone deal double damage.
• Attacks, spells, and abilities that are designed to kill you in one hit, either by depleting your HP down to 0 or automatically killing you instead reduce your HP to 1, and you gain +5 AC until the start of your next turn. This does not apply to standard damage.