Demon Slayer: Mouth Breathing

Demon Slayers are a tradition of warriors who focus on purely martial techniques to combat fiendish forces. Their training is rigorous and centers on their breath and breathing, controlling them to enhance their potential and perform techniques reminiscent of various elements. There was originally only one style, Sun Breathing, but its athletic demands proved to be too much for most Demon Slayers, and so other styles began to develop.

Mouth Breathing is based on not an element but the motions and tactics of mouth breathers, mythical creatures thought to be feral humans that are stealthy stalkers who use paranoia to unsettle their targets when threatened. An offshoot of Wind Breathing- a style that mimics the motions of the wind itself, using whirlwind slashes and high-speed movement- Mouth Breathing also focuses on high-speed movement, but channels the mimicry of wind into ventriloquism. Mouth Breathers throw their voice and use misdirection to open up their target's defenses for wind-swift slashes, and to keep their foes guessing as to where they really are, leaving behind only the unsettling sound of their mouth breathing.

As a practitioner of Mouth Breathing, you likely spent time training in a Demon Slayer temple, and perhaps even grew up in one. Regardless of your alignment, you will probably have a strict and idiosyncratic code of honor influenced by your time amongst others of the order. Having left the temple, on a simple mission or maybe because of a personal vendetta against a particular fiend, it is up to you to represent your order well and to confront its foes.

Demon Slayer

Beginning when you choose this archetype at 3rd level, your study of the lore of Fiends lets you treat Fiends as a favored enemy.

Armor of any kind or shields would make your athletic maneuvers impossible, and so those of the Demon Slayer order simply just don't wear any. However, their immense athleticism and combat prowess offers its own protection. Your unarmored AC equals 13+your Dexterity modifier. Though Demon Slayers don't cast actual magic, their abilities that do require the target to make a saving throw use their Strength, because the forms of the order are based on athleticism and breath control.

You can also enter a Total Concentration Breathing Stance as an action, heightening your focus on technique. While in the stance, for the next minute your melee weapon attacks count as magical, and while conscious and not Incapacitated you have advantage on Dexterity saving throws against effects you can see. In addition, your other Demon Slayer features have extra effects while in the stance.

Form 1: Sock Puppet

The first form of Mouth Breathing is the Sock Puppet mimicry technique, where the slayer changes and/or throws their voice to create the illusion that something else is happening when it's really just them. This is used to create distractions, making an opening to escape, or attack.

You gain the Minor Illusion cantrip, and proficiency in Stealth and Deception. Minor Illusion can only be used to create sounds but does not require its material or somatic components, but instead uses a vocal component; you can also dismiss it as no action. If you cast Minor Illusion with this feature while using Total Concentration Breathing, you have advantage on Stealth checks to Hide until the end of your next turn.

Form 2: Jump Scare

Starting at 7th level, you have learned to emulate some of the movement techniques of mouth breathers, who use sudden motions to confuse and frighten their targets. You add half your proficiency to your Initiative, and can Dash, Disengage, or Dodge as a bonus action during your turn. Also, if you move at least half your speed, you become partially obscured until the end of your next turn or until you make an attack.

In addition, when you are in the Total Concentration Breathing stance and if you are hidden or partially obscured when you make an attack, then once during your turn you can deal bonus damage equal to half your Fiend Fighter level on a weapon attack.

Form 5: Ban Evasion

At 10th level, you have become as tricky to pin down as a real mouth breather, your breath control making your movements sharper and more efficient, and your senses clearer. Opportunity attacks against you have disadvantage while you are conscious and not incapacitated, and you can move stealthily at a normal speed. In addition, if you are in the Total Concentration Breathing stance and successfully take the Hide action, you can make a saving throw against one condition affecting you.

Form 6: VPN

Starting at 15th level, you have studied the ways of Vigilant Paranormal Neutralization from the lore of your order, and are permanently under the effects of the Protection from Evil and Good spell. Additionally, while in the Total Concentration Breathing stance, when you hit a target with a weapon attack, it is considered to be under the effects of the Bane spell; this ends on one target when you attack a new one.

Form 8: Gaslight

At 18th level, you have learned to put together various techniques into one, using subtle movements, deception, and sound to convince your opponent that they are outnumbered- convincingly enough so that, like the mythical mouth breathers, you can seemingly vanish into thin air when your opponent takes the bait.

You gain an Aura out to 10 feet. Whenever a creature(s) enters the aura, it must make an Intelligence saving throw against your spell save DC: if it fails, until the end of your next turn it is considered to be flanked when you make a weapon attack against it, and you regain Proficiency+5 HP if you have no more than half(and not 0) of your HP left. While in the Total Concentration Breathing stance, if an ally hits a creature in your aura with a weapon attack,  as a reaction you can become Invisible until the start of your next turn and take the Disengage action.