A secret Illuminati-esque society has accidentally summoned an omnimalevolent demon into our world, and they lost control of it. To avoid discovery, the society decided to seal away the demon in a random unlucky individual (that's you). The spell keeping the demon trapped in your body will gradually melt down it's body and allow you to claim it's abilities for yourself in a year's time, but in the mean time you must endure it's rage.
Whenever you regain consciousness(like when you wake up), there is a chance that the demon will gain control of your body and will wreck havoc for 2 hours. What percent chance of the demon taking you ask? Well...
Build your demon:
These are the powers that you demon possesses and the ones you will inherit (you won't gain Demon Physiology and Omnimalevolence). This will also calculate the percentage of your demon taking over (if a power fits into more than one category then you only add the largest percentage instead of all of them). At 100% they can take over your body whenever. The percentage is also the chances of them deciding to not torture you when in control and to instead target the world around you.
5% Base Chance
+1% Real Powers
+5% Peak Human or Enhanced Condition
+10% Supernatural Condition
+15% Simple and weak abilities (like Pyrokinesis)
+20% Umbrella Powers
+20% Science Powers
+25% Powers relating to Mythical Beings and Magic
+45% Omni-Powers (Except Omni-Manipulation and Omnipotence, the latter isn't allowed)
+50% Absolute and Almighty Powers
+60% Powers ending with -potence or -science
+60% Transcendent Powers
+70% Meta Powers
If your power doesn't apply directly to one of these powers, I trust you to give it a reasonable percentage addition.