They stand in the forest, looking each other deep into the eyes. A voice starts speaking in his head: "You are a fitting host. You shall be granted power in exchange for being my vessel." The guy, clearly in shock due to this fateful meeting, pulls himself together to nod his head. The voice speaks up again: "So it shall be" and the creature before him vanishes. He can feel a new pounding inside his chest.

A new soul.

A new creature.

A partner for life.

You are not made to be a Mythical Beast, you are chosen to be one by the Beast itself. It will find you if you are fitting but you won't find it no matter how long you keep searching for it. Once it found you, you can either agree to its conditions or be taken over by the Beast forcefully. Nobody has ever been able to resist the power of a Beast and only very few share a body with one because these Beasts are almost extinct from the world. While traveling with your Beast the two of you will slowly but surely gain more access to the features of each other. Therefore the Beast grants you more power while you grant it a greater access over your body. The longer you travel with it the deeper the bound of trust between the two of you becomes.

Eyes of the Beast

At 1st level when you look someone directly in the eyes while you are no more than 5 feet apart from each other and you are speaking with that person you can make them see a glimmer of the beast inside you, giving you advantage on Intimidation checks but the person spoken with automatically assumes that you are of evil alignment.

Natural Armor

At 1st level due to the agility of your inner beast your AC equals 10 + your Dexterity modifier + your Proficiency while wearing no armor.

Unforgiving Slash

At 1st level you choose one hand. The chosen hand transforms into a claw-like hand equaling that of your inner beast with no way to revert this transformation. This is treated as a natural weapon which you are proficient with, with the finesse property dealing 1d6 necrotic damage if you are of evil alignment or 1d6 radiant damage if you are of good alignment. The damage dealt increases to 1d8 at 5th level, 1d10 at 9th level, 2d6 at 13th level and 2d8 at 17th level

Unforgiving Slash - Evil

1d6 necrotic damage if you are of evil alignment

Unforgiving Slash - Good

1d6 radiant damage if you are of good alignment

Power of the Beast

At 2nd level your inner Beast starts to grant you access to its powers. You can call upon its powers using a bonus action to double all damage dealt with your Unforgiving Slash until the start of your next turn. Afterwards enemies attacking you have advantage on their attacks until the end of your next turn. You can use this feature twice before you must finish a short or long rest to regain all uses of this feature.

Elemental Slash

At 2nd level as a bonus action you can infuse your Unforgiving Slash with an element of your choice for 1 round dealing 1d4 additional damage in the type of your chosen element.

Choose Your Path

At 3rd level you have to choose a way of the two ways shown below in the Path of Trust column.

Way of Creation

The Way of Creation determines the mutual goal for you and your Beast to be the Creation of a deep bond between the two of you. Your Beast slowly offers you more powers while you give it control over your body in little steps. Due to the deep bond and the careful approach you and your Beast are taking your bond is developing very nicely.

Following the Way of Creation you will get Points of Creation. Gathering 10 points of Creation allows you to cast the spell "Mass Cure Wounds" once using up 10 points of creation. You cannot gather more than 10 points of creation.

Way of Destruction

The Way of Destruction determines the mutual goal for you and your Beast to be the Destruction of your enemies. Your Beast offers you even greater powers while you give it control over more and more of your body. Due to the great amount of power you receive and the toll it takes on your body this way will damage you after using its powers in a fight.

Following the Way of Destruction will give you Points of Destruction as you use its features. When you reach 10 Points of Destruction, you will suffer one level of exhaustion, and your point count will be reset to 0. Completing a long rest will remove 3 points.

Instincts of Nature

At 3rd level when an enemy attacks you, you can use your reaction to make a Dexterity saving throw with a DC equal to 8 + half of the attack roll. If you succeed you only take half of the total damage. This can be used against melee, ranged and spell attacks but does not work against a critical hit or attacks that require you to make a saving throw.

Ability Score Increase

When you reach 4th level, and again at 8th, 12th, 16th and 19th level, you can increase one ability score of your choice by 2, or you can increase two ability scores of your choice by 1. As normal, you can't increase an ability score above 20 using this feature.

Beast Mode

At 5th level your beast grants you access to its body for up to 1 minute. When you activate this feature as a bonus action your body turns into that of your inner Beast making it either a bright werewolf shaped body if you are of good alignment or a dark werewolf shaped body if you are of evil alignment. You gain blindsight for 10 feet. Your Unforgiving Slash damage die increases to the next higher one and you can use this feature with both hands. You also gain an additional 20 feet speed and can attack with your Unforgiving Slash using a bonus action. You may choose one element to deal damage with like described in your Elemental Slash feature for the whole minute. After a number of rounds equal to your Intelligence Modifier (minimum of 1) you must make an Intelligence saving throw equal to 8 + half your Intelligence Modifier or go insane. You remain insane until the minute is over. While you are insane you attack a creature that you can see, chosen randomly by the GM with your Unforgiving Slashes with disadvantage on the attack roll and maximum damage possible on hit. You attack as often as your attack action allows you to. When the chosen enemy is out of your normal moving range you teleport the remaining distance, moving to an unoccupied space within 5 feet of the target. After attacking you teleport back to the space you teleported from. If there is no unoccupied space you are teleported into the space of another creature dealing your attacks to this creature instead before returning to the point you teleported from. You return to normal after the minute is over or when you drop to 0 hit points. You can also choose to leave the Beast Mode as a bonus action. If you choose to leave the Beast Mode you must make an Intelligence Check with a DC equal to 8 + your Proficiency. On a failed save you remain in the Beast Mode. On a successful save you leave the Beast Mode. You cannot choose to leave the Beast Mode when you went insane. When you regain your normal form you gain 1 level of exhaustion. If you went insane during the Beast Mode you need to consume a day of food and water within the next 10 minutes or receive another level of exhaustion.

At 20th level you no longer suffer a level of exhaustion or need to eat after you leave the Beast Mode. You can also willingly leave the Beast Mode without requiring a Check regardless of whether you went insane or not. You also do not need to roll for insanity. You can still choose to go insane but you can control who you want to attack when insane. Once you went insane you cannot go back unless you leave the Beast Mode. Your blindsight improves to 60 feet and you gain a total of 60 additional flying speed with either dark wings if you are of evil alignment or bright wings if you are of good alignment that you develop in the Beast Mode.

Extra Attack

Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn. This number rises to 3 at 10th level and 4 at 15th level.

Senses of the Beast

At 6th level when you are fighting a humanoid enemy or an enemy with an intelligence lower than 11 you can predict their actions to some extent. When such an enemy makes a melee attack on you, you can use your reaction to roll a Dexterity Check. If your roll is equal to or higher than the attackers attack bonus you can repel his attack forcing it to miss. Then you can attack that enemy with advantage on the attack roll. You can only use this feature twice before you must finish a long rest to regain all uses of this feature.

Mythical Roar

At 11th level you can use the voice of your inner beast to make a frightening Roar. When you activate this feature as an action all enemies within a 60 feet radius who can hear you must make a Wisdom saving throw equal to 8 + your Proficiency + your Intelligence Modifier. On a failed save a creature is frightened for 1 minute and takes 4d12 psychic damage. A frightened target can repeat the saving throw at the end of each of its turns. On a successful save a creature takes half damage and is not frightened. A humanoid enemy or an enemy with less than 10 Intelligence has disadvantage on the saving throw and takes 2d12 extra psychic damage. An enemy with less than 5 Intelligence automatically fails the save and takes 2d12 extra psychic damage as well. Fail or success, creatures who heard your Roar are immune to its frightening effect for the next 6 hours. You can only use this feature once per combat.

Cuts of the Beast

At 14th level you can temporarily give your inner Beast control over your body to make multiple Cut attacks against an enemy. When you activate this feature as an action choose an enemy within your range of movement. You must make an Intelligence Check equal to 8 + half the Challenge Rating of the chosen enemy. On a successful check your inner Beast takes over your body and teleports to the chosen enemy, making 10 cuts with your attack bonus + 5. You cannot land a critical hit or a critical failure on these cuts. For every cut the chosen enemy takes your Unforgiving Slash damage. The enemy can roll a Dexterity saving throw with a DC equal to 8 + your Proficiency + your Dexterity Modifier. On a successful save he only takes half damage. When the chosen enemy is of a different alignment than you, you make 5 additional cuts. You must finish a long rest to regain all uses of this feature.

All-In

At 18th level you can push your body beyond its normal limits to make an attack using your Unforgiving Slash feature together with your Elemental Slash feature. Then you can create a Mythical Roar and to finish it off you can use your Cuts of the Beast feature, disregarding whether you can use this feature at that moment or not. You have to use your whole turn (including your reaction) for this feature and you must roll a Constitution saving throw with a DC equal to 8 + your Proficiency or suffer a level of exhaustion.