Curse of The Great Beast

Transform:

On your turn, you transform as a bonus action. At the end of your turn while you're transformed, you take 2d12 - Constitution Modifier of force damage

You may use this transformation for an equal amount of time equal to your proficiency bonus.

While transformed, you gain the following benefits:

• Your speed becomes 40, or you gain +5 feet to your speed, whichever is greater.
• When you make an attack you roll an additional 1d6 and add that to the Attack roll.
• You have advantage on Dexterity saving throws and ability checks. 

Heightened Mind and Body:

While transformed and not wearing armor or a shield, your AC becomes 13 + Wisdom ability modifier (minimum of 1) + Dexterity ability modifier (minimum of 1). 

Soul Hide (Bonus Action, 3 charges):

The unearthly sheen resolves into screaming faces periodically, as if tortured souls are crawling on your skin.

When you use your Transformation you can use youre bonus action to gain temporary hit points equal to an amount equal to your hit die + Constitution modifier + 1d6.

Sonic Scream (Bonus Action, Recharge 6):

As a bonus action, you can unleash an unnerving scream – such as a high-pitched scream, a howl, or a furious roar. You can cast Thunderwave as a 5th-level spell. 

Side Effects:

As the creature loses hit points, the mark begins to take control over the user. If the creature reaches 0 hit points while still having the mark, its true effects come to bloom, and the great beast would induce its wrath.

The creature has disadvantage on death saving throws while the mark on them is active. Upon dying, the creature becomes the plaything of the god who enacted the curse, and the mark is permanent, even if the creature leaves the affected area. The exact details of what happens at death depend on the gods who use it, and differ based on that.

Inner Beast / Unstoppable Monster:

If you have succesfully defeated The Caprathorn you gain the following effect:

• You are on constant guard to try and contain your curse. While not transformed, you have advantage on saving throws against the charmed and frightened condition, and have resistance to psychic damage. 
• Your curse has made you incredibly difficult to kill. Whenever you would be reduced to 0 hit points, you can spend your reaction to restore yourself to half of your maximum hit points (rounded down). When you do so, you reduce the number of death saving throws you need to fail in order to die by one. If you have no death saving throws remaining, you instantly die the next time you fall to 0 hit points. If the d20 roll for your death saving throw is a 20, you increase the number of death saving throws you need to fail in order to die by one, to a maximum of three.

Removing Mark:

This mark cannot be removed by remove curse within the affected area. Only wish may have any effect, and even then, a DM may rule it cannot overpower a divine mandate.