Nullifier

You have been trained to exert your own will over others, specifically in the realm of magic practitioners.  As a nullifier, you have trained and honed your martial skills to avoid magical attacks and to end the concentration of those who cast spells.  Your physical body and will are as much of a weapons as they are defenses to magic users.  You may even learn to shield your allies from magical attacks and spells.

Bonus Proficiencies

When you choose this archetype at 3rd level, you gain proficiency in one of the following skills of your choice: Arcana, Insight, Religion, or Perception. Alternatively, you learn one language of your choice.

Nullifying Strike

Beginning at 3rd level, you have learned the ways to counter magic in the world.  When you hit with a weapon attack against a creature that has a spell affecting it or is concentrating on a spell, you may make a Wisdom check against the DC of the spellcaster to end the effect early.  You may attempt to end one effect per Attack action in this way.

Nullifying Reflex

Starting at 7th level, your ability to anticipate magical attacks is further developed.  When a spell attack is made against you that you can see or hear, you may use your reaction to gain a bonus to your armor class equal to your Wisdom modifier until the start of your next turn.  Once you use this feature, you can't do so again until you finish a short or long rest.

Additional Fighting Style

At 10th level, you can choose a second option from the Fighting Style class feature.

Archery

You gain a +2 bonus to attack rolls you make with ranged weapons.

Defense

While you are wearing armor, you gain a +1 bonus to AC.

Dueling

When you are wielding a melee weapon in one hand and no other weapons, you gain a +2 bonus to damage rolls with that weapon.

Great Weapon Fighting

When you roll a 1 or 2 on a damage die for an attack you make with a melee weapon that you are wielding with two hands, you can reroll the die and must use the new roll, even if the new roll is a 1 or a 2. The weapon must have the two-handed or versatile property for you to gain this benefit.

Protection

When a creature you can see attacks a target other than you that is within 5 feet of you, you can use your reaction to impose disadvantage on the attack roll. You must be wielding a shield.

Two-Weapon Fighting

When you engage in two-weapon fighting, you can add your ability modifier to the damage of the second attack.

Situational Awareness

Starting at 15th level, your ability to read situations have heightened even further.  You may also add your Wisdom modifier to your initiative rolls.

Nullifier Bulwark

At 18th level, your defensive abilities become the pinnacle against magical attacks.  When you or an ally within 5 feet are hit from a spell attack or fail a saving throw from a spell, you may choose have the spell attack miss or succeed the saving throw instead.  You regain use of this feature when you complete a long rest.