Demonic Possession

You have been possessed by a demon.                       

you can call on this power as an action once per long rest. 

you can use your action to unleash the demonic energy within yourself, causing your eyes to turn into pools of darkness and two shadowy, flightless wings to sprout from your back. black shadow energy seeps from your body.

while in this demon form you are resistant do non magical damage however you are vulnerable to radiant damage. 

Your transformation lasts for 1 minute (or higher) or until you end it as a bonus action. During it, once on each of your turns, you can deal extra necrotic damage to one target when you deal damage to it with an attack or a spell.

 The extra necrotic damage equals:

1d4 from level 1.

2d4 from level 5.

3d4 from level 11.

4d4 from level 17

the time also increases with level as you grain control over this power:

1 minute from level 1.

2 minutes from level 5.

3 minutes from level 11.

4 minutes from level 17

HOWEVER! demonic power is nothing to mess with, every time you call upon this power you must roll % die or d100.

on a 1 you are completely overtaken by the power of the demon and your character is considered dead.

after level 11 the power will no longer kill you but you will suffer 3 points of exhaustion.

from level 17 you will only suffer 1 point of exhaustion.