Demonic Possession

A demonic soul inhabits your body. It is mostly inert, but the sight of blood and violence causes it to stir and try to rest control of the body away from the host. 

At the end of each battle or when the character kills an opponent roll a 1d20:

1- Demon fights the host for control, see below for the effect

2 - 20 - No effect

On a roll of one the battle for possession begins, as the demon exerts control, the character will roll twice against a list of abilities, ordered at the characters choosing, and assign a number for each ability from 1 through 6. For example:

1. Strength
2. Dexterity
3. Constitution
4. Intelligence
5. Wisdom
6. Charisma

You will roll a 1d6 against this list. The first roll will be a +1 to that ability, the second roll will be a -1 to that ability. Max for any stat will be 20 and minimum will be 3. The duration will be one hour from the last roll, so if you roll a 1 on a 1d20 after a battle, roll to increase/decrease stats and this will be in effect for one hour. After the hour your stats will go back to normal. If you roll another one on a 1d20 before the one hour duration then the effects will add on, so there's a possibility you may have a +4 on a stat and a -4 on another, but when this happens again then the one hour duration resets. 

The key stats for this feat will be Wisdom or Intelligence. If at anytime during this "battle" if you have your Wisdom or Intelligence ability at +2 then the host gains control and can either continue with the plus and minus stats until their next long rest or they can banish the demon to the deepest corner of their mind until the next long rest at which point the stats will go back to normal. Either way, until the next long rest, the character no longer has to roll a 1d20 after each battle or death dealt by the character.

If Wisdom or Intelligence reaches -2, the demon takes complete control for an hour and enters a bloodlust rage keeping the enhanced stats and will attack anything and everything within sight, treat the first attack as a surprise attack on the closest living entity.