Wondrous Item, very rare (requires attunement by a monk)
The armband was carved from the remnant shell of an ancient elder earth elemental, with four embedded elemental crystals and primordial runes etched deep into the band. During a short rest, the armband can be attuned to one of the four elements, channeling your ki through the elemental crystals to provide extra damage to your unarmed strikes. The armband maintains its connection to an element until you fall unconscious or change it over the course of another short rest. While you are attuned to fire, you can ignite one or both of your hands (no action required), becoming a light source that sheds bright light in a 10-foot radius and dim light for an additional 10 feet. 

Element's Strength. While attuned to an element, you gain access to its cantrip. Cantrips use your ki save and can used once per hour. As a bonus action, you can spend ki points to imbue your unarmed strikes with the attuned element to deal bonus damage equal to your Martial Arts die for 1 minute. The ki point cost is equal to half your martial arts die (i.e. 1d4 = 2 ki, 1d6 = 3 ki, 1d8 = 4 ki, 1d10 = 5 ki). The cantrip and damage type is determined by the attuned element according to the table below:

| Element | Damage Type |     Cantrip     |
|-----------------------------------------|
|  Air    |  Lightning  |  Gust           |
|  Earth  |  Thunder    |  Mold Earth     |
|  Fire   |  Fire       |  Control Flame  |
|  Water  |  Cold       |  Shape Water    |

Element's Wrath. The armband has 3 charges and regains all expended charges daily at dawn. Before you make an unarmed strike while Element's Strength is active, you can expend 1 charge to further empower the attack. If the attack hits, the creature must succeed on a saving throw against your ki save DC or it suffers an additional effect based on the attuned element.

  • Air. Target must succeed on Constitution saving throw or be stunned until the end of your next turn.
  • Earth. Target must succeed on a Strength saving throw or be knocked prone until the end of your next turn.
  • Fire. Target must succeed on a Dexterity saving throw or it catches fire. Until a creature takes an action to douse the fire, the target takes 1d10 fire damage at the start of each of its turns.
  • Water. Target must succeed on a Constitution saving throw or have its speed reduced by 20 feet until the end of your next turn.

"You misunderstand the purpose of the armband and our exercises, young monk. The armband is merely a tool to deepen our connection to the elements, not a source of power. Our Material Plane is a combination of the four Elemental Planes and everything we see is made from the elements, from the fire that keeps us warm, to the air we breathe, the water we drink, and the earth we stand upon. To achieve true enlightenment, we must strive to know the elements as we know ourselves because it is only then that we may begin to understand our world and the Material Plane. These exercises are meant to focus our lifeforce and ki through the crystals of the armband, so we may more easily channel the elements through ourselves." -Grandmaster Genki explaining the armband to a young monk

 

Notes: Speed Reduction: Impose, Damage: Fire, Damage: Fire, Damage: Cold, Damage: Lightning, Damage: Thunder, Stunned, Prone, monk

GrayStag