Psionic Warrior

The Psionic Warrior is a master of their own mind. Practitioners of this archetype follow an ancient tradition thought to be based on the style of the fierce Githyanki. Psionic Warriors excel in defending themselves from physical and mental attacks, and can focus their minds so keenly that their will creates physical barriers protecting the warriors. The skills of the Psionic Warrior are a dying art, and, outside of the Githyanki, Psionic Warriors are rare. Those who truly follow this tradition can find employ anywhere a trained warrior can, and sometimes in places one normally couldn't, their mental defenses allowing them to go toe-to-toe with enemies that would cause equally physically powerful warriors to quake in their boots.

Psionic Attunement

Starting when you choose this archetype at 3rd level, your deep self-knowledge and psionic affinity gives you a unique insight into the workings of the Weave. You gain proficiency in the Arcana skill. Your proficiency bonus is doubled for any ability check that uses this skill.

In addition, you learn the Detect Magic spell, which you can cast only as a ritual.

Mental Defense

Also at 3rd level, you learn to manifest your will as a psychic barrier, protecting you at the cost of lessening your offensive capabilities.

The first time you make a weapon attack on your turn, you may take a penalty to your weapon attack bonus (up to half your Fighter level, rounded up). You gain a bonus to your AC equal to the penalty to your weapon attack bonus. The adjusted bonuses remain in effect until the start of your next turn. You must take an additional penalty to your attack bonus to activate other features that trigger on taking a penalty to your attack bonus.

Psionic Barrage

At 7th level, you learn to infuse your blows with psionic energy, harming both your enemies' physical forms and their psyches.

You may use your bonus action on your turn to cause your weapon attacks to deal an extra 1d6 psychic damage on a hit until the end of your turn. In addition, if these attacks use a nonmagical weapon, the damage from this weapon counts as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage until the end of your turn.

You can use this feature a number of times equal to your Intelligence modifier (minimum of once). You regain all expended uses of it once you finish a long rest.

Thought Shield

Starting at 10th level, your self-discipline has honed your mental defenses. You gain proficiency in Wisdom saving throws. If you already have this proficiency, you instead gain proficiency in Intelligence or Charisma saving throws (your choice).

In addition, your mastery over your psyche has granted you the ability to use your own pain to snap yourself out of harmful mental states. Once on each of your turns if you are under an effect that causes you to be charmed, frightened, paralyzed, or stunned, you may take psychic damage equal to your Fighter level. This damage cannot be reduced or prevented in any way. Immediately after taking this damage, you may make a saving throw with advantage against the effect. If the effect does not require saving throws to end it, you end it without any saving throw.

Psychic Onslaught

Starting at 15th level, you are able to focus your mind on delivering one terrible blow to your foe, striking both their mind and body with staggering power.

As an action, you may make a single weapon attack against a foe, using your weapon's normal reach or range. On a hit, the target suffers the attack's normal effects, and must make an Intelligence saving throw (DC 8 + your proficiency bonus + your Intelligence modifier). A creature that fails this saving throw takes psychic damage equal to your Fighter level, and is stunned until the end of your next turn. A creature that succeeds on its saving throw takes half as much psychic damage, and is not stunned.

Psychic Retaliation

Starting at 18th level, your mental defenses increase, manifesting in a psychic barrier that punishes your foes when they harm you. When a creature hits you with an attack, that creature takes psychic damage equal to your Intelligence modifier. In addition, you may use your reaction to give that creature disadvantage on attack rolls until the end of its turn.