Curse Mark Corruption

You've been mysteriously marked with a series of twelve small tattoos that manifest along your spine from corruption.  In moments of weakness and situations that demands immense strength, a cold and convincing voice within your mind assures that they can supply it.

Any Curse Mark features used throughout the day, bargains made in times of strife, or giving into the curse in any form will warrant a Constitution saving throw DC 18 at the end of the of the day before or during a long rest. You may forgo the saving throw if you so desire the furthering of corruption. You may only have up to ten points of corruption (PoC) at any given point in time. 

Corruption points can only be removed by the spell effects of Greater Restoration and Wish.

Each consecutive PoC adds a permanent -1 penalty to any rolls made to save against the effects of corruption. The total negative penalty is unchanged even if the PoC have been magically removed. 

1.  First PoC: You obtain dark vision or superior dark vision if you already have the ability to see in the dark.
2. Second PoC: By tapping into a sinister darkness within, you may use one of your barbarian rages to enter a state that sports a dark aura around your person. Dark mode effectively lasts as long as a typical rage would. While in dark mode you may add an additional 1d4 of necrotic damage to any attack roll.
3. Third PoC: You gain the ability to harness the darkness inside you to manifest a deadly shadow stitching attack on foes around you. When you have made an attack that has been declared a hit, you may choose to make it a Stitching Shadow  attack.

   Before you have made an attack that has been declared a hit, you may choose to make it a Stitching Shadow Strike.

   Force your target and any creature within a 5ft sphere of them to make Dexterity saving throws DC (8+Proficiency Bonus+Total PoC) or take an extra 1d8 necrotic damage. Additionally, if the target failed saving throw or be slowed until the spell ends. As an action, the creature may make an Acrobatics/Athletics check against your spell save DC to steel its resolve and end this spell.

   Every rage point used adds an extra 1d8 to the spells damage and an additional 5ft.

4. Forth PoC: Your dark mode damage die is increased to a d6. Your eyes are also turn to a familiar orange and hair to dark black color.
5. Fifth PoC: While in dark mode your movement speed increases by 10ft. Additionally, If an 18 or 19 are rolled they are to be considered critical hits. Once you have reached 5 PoC the minimum amount of corruption that can be removed is up to stage 3.
6. Sixth PoC: Your dark mode damage die is increased to a d8. If not already sporting these features, a pointed goatee will grow in and ears will also start to come to a point. 
7. Seventh PoC: If you are in dark mode and land a critical hit on a target, one use of rage recharges.
8. Eighth PoC: You're dark mode damage die increases to a d10. You've learned how to manifest several modes of darkness at its boiling point and can lob them in quick succession at ranged foes. By spending one use of your rage you can cast Dark Volley as an action to make 3 ranged spell attacks (Proficiency Bonus+Total PoC) on any target within 30ft of you. On a hit, the target takes 1d12 necrotic damage. Every additional rage point used for Dark Volley adds two extra spell attacks
9. Ninth PoC: You're dark mode damage die increases to a d12. Your martial prowess and strength are just about at its peak. When you make an attack on a target that exceeds their AC by 10 or more you may add an additional 1d12 after damage calculation. Once you have reached 9 PoC the minimum amount of corruption that can be removed is up to stage 6.
10. Tenth PoC: ? ? ?