You transform one of your arms into a tendril of pure dark magic. You make a attack roll and on impact it does 3D10 piercing damage. 

Add 1D10 per level.

the more you use this spell the more the arm you cast this spell on becomes more imbued with dark magic. First 1 times you use this spell nothing happens.

2nd time- your arm starts to turn a dark shade of grey and veins start to become dark red.

3rd time- your arm is a dark grey. The virus starts to go further then your arm and to your head and torso. You start hearing dark thoughts as if another voice is speaking to you.

4th time- most of your body is a dark grey almost black. Your eyes get a glint of red in them and that small voice becomes louder and it’s suggestions aren’t so dark anymore.

5th time- your whole body is black, your eyes glow with an evil red. This spell can be cast at will at its lowest level. You no longer can fully control your body. Sometimes you are just a passenger in your body watching as something else is in control. You can make a DC 18 intelligence saving throw to try and take control.

6th time- you no longer have control over your body. The only way you can get control is if you make a DC 25 intelligence saving throw. If you succeed on it you must make intelligence saving throws every 10 minutes to stay in control.