This devil fruit is purple in color, with strange swirls covering it. It seems to suck in everything near it, light, your eyes..

This glowing fruit has a strange feeling, being much heavier than it looks, being almost impossible to lift

The fruit will scale (separate from player level, depends on use and experience, up to level 5)

1st Level: Your body becomes comprised of Darkness, and you can activate your darkness form once per short rest for an hour. In this form, you gain resistance to nonmagical damage, and ranged attacks against you have advantage as your darkness sucks in everything nearby. You also gain magic missile 3x per short rest @ level 2, darkness 2x per long rest, and witch bolt 3x per short rest, all deal necrotic damage, as they are made from your shadows and darkness. Your touch also nullifies the power of devil fruit users, though this ends when you are no longer touching them.

2nd Level: Your control over darkness increases, you are able to cast Shadow of Moil on yourself, 1x per short rest, Hold person 2x @ level 3 per short rest, and hold monster 1x per long rest. You holding a monster or person is flavored as the darkness sucking them up and holding them in the black hole. They take 3d6 damage at the end of their turn if not released by a DC 15 strength check. You can also infuse attacks with darkness, casting shadow blade on anything 2x per short rest as a bonus action. 

3rd Level: Your control over darkness increases, as an action, you can choose to suck in objects from around you, and spit them out on the next turn. This "Liberation" does Xd8 damage depending on what is brought inside, and is a bonus action. The sucking is a demisphere around you with a radius of 20 ft. This increases by 5 ft every level of the fruit. Depending on the object, starting with medium the strength saving throw would be a DC 15, with it increasing the more you bring in, and the larger the object.  If one of your shadow infused attacks hits a devil fruit user, they lose their powers for 1 min. 

4th Level: If a ranged attack misses your AC, you can absorb it into your darkness and return it to sender as a reaction. This counts for spells as well, equal to the fruit's level. 

5th Level: You are one with the darkness, it is you, and you are it. You can now cast Maddening darkness 1x per long rest, and absorb the power of one devil fruit in addition to the Yami yami no mi. You can only do this once, and it must be taken from the corpse of a devil fruit user. However, when you absorb it, you gain the fruit level of their own experience. You can level up the fruit once you absorb it. You cannot replace the new fruit.