Monks are known to be pure hearted and with good intent, doing usually what's best for the others around them. But these Monks who go in the tradition of the Way of the Monsters, well, they don't always have the best intent. Monks who go along this path start to look more like monstrous humanoids. Unhinged jaws, claws the sharper than swords and twisted looks, they make eldritch horrors look like puppies and kittens. The once humanoids were normal, but then they sought power, or had to adapt to the conditions they were in, that be too long in the Shadowfell or in an environment of despair and darkness.

Darkness Unfolds

Starting at 3rd level, when you pick this tradition, you start your transformation and grow retractable claws from your hands. These claws deal the same amount of damage as your Unarmed Strikes but deal Slashing damage instead of Bludgeoning damage. You also gain darkvision out to 60 feet. At 19th level, the claws deal 1d12 damage instead of 1d10.

Dark Engaging

Starting at 6th level, you start to embrace the slight monster in your body and become best in darkness. If you are in dim light or complete darkness, you don't get disadvantage with perception checks in dim light. Additionally, you gain advantage on initiative rolls while in dim lights or darkness, and you can now use 1 ki point to cast Darkness without material components.

Monstrous Disappearance

Starting at 11th level, you can spend 1 ki to turn invisible when in dim light or darkness. You stay invisible until you step into bright light, decide to turn visible again, attack a creature or cast a spell that deals damage. You can also use an action to make your eyes glow a bright yellow. This gives you 30 feet of blindsight, but makes perception checks to find you have advantage.

Unleash the Beast

Starting at 17th level, at the cost of 3 ki points, you unleash the beast within you, turning into a large humanoid abomination of a creature, known as the monster form. This form lasts for 5 minutes or until you decided to stop being a monster. While in this form, your movement speed becomes 90 feet, and your claws now deal 3d10 + your dexterity or strength modifier while in this form, and you can, as an action you can vomit a slick, tarry goo in a 30-foot-long, 5-foot wide line. Everyone in that line must make a DEX saving throw [DC = 10 + your Monk Level] or take 4d12 acid damage and be restrained by the tarry substance for 1d4 rounds. If they succeed, they take half damage and do not get restrained. Hit or not, the floor that was hit by the vomit is sticky with the goo becomes difficult terrain for 5 minutes or until it is cleaned thoroughly. You may also bite as an attack, dealing 3d12 + your strength modifier piercing damage. When you enter this from, you can only use these attacks, you cannot use any other attacks, but you can use other actions such as dashing or using a charge of a magic item that doesn't deal damage.