Path of Fundamental Chaos

'''Note: This class has not been published, and is based on observed abilities during game play. It is incomplete and subject to change.'''

The Path of the Fundamental Chaos is the barbarian subclass of Ashton Greymoore. It is implied to be connected to dunamancy, as Ashton's head injury was healed with, among other things, a vial of dunamantic potion.

Chaos Burst
Upon choosing this path at level 3, a Fundamental Chaos barbarian can choose to deal extra damage on an attack with a chaos burst. This allows them to add 2d4 damage to an attack with a melee weapon twice a day. Damage type depends on a rolled die and includes lightning, force, cold, fire, and psychic.

Rage Type
Also at level 3, the rage type is determined randomly by rolling 1d4 whenever the barbarian begins their rage:
 * Orbital Decay (Gravity): When raging, gravity seems to have more of a pull for everyone in the room (including allies). Enemies within 15 feet are pulled up to 10 feet toward the barbarian and suffer disadvantage on attacks against creatures other than the barbarian.
 * Temporal Morass (Time): The barbarian may choose a target, who must make a Constitution saving throw to avoid having their speed halved and losing their reactions.
 * Space: When the barbarian makes a melee attack, they can open a portal to a space within 60 feet that they can see and attack a creature as though the barbarian were in that space.
 * Luck: Each ally within 15 feet of the barbarian can add a d4 to attack rolls and saving throws.

Hyper Rage
At level 6, while raging, the barbarian can enter a hyper rage on their turn, presumably with different effects for which type of rage is active. They can do this a limited number of times per day.
 * Time: The barbarian can make an additional attack as part of the Attack action.

Behind the scenes
Taliesin Jaffe asked Matthew Mercer if he could homebrew a barbarian class, as he was dissatisfied the Path of Wild Magic barbarian from Tasha's Cauldron of Everything, in which your powers of chaos become more controlled as you level up. He wanted a class that was more chaotic and unpredictable. The process of creating the class was collaborative.