The drunk dragon
A long time ago in a dimension not so far away (you just go step through the portal and take the second unravelling of impossibility to the left), there was a mighty dragon called Kalewynn, first and greatest of all Necromancers. So great was his power that even his dimensional neighbours began to have trouble sleeping for some of their eon-long slumbers. Even demons avoided the big scaly bastard. He was great, he was huge, and he was a real badass.
He's also been dead for about 16.000 years...
A few years ago, a young jobless slacker fanboy, with a penchant for Lovecraft and the occult, decided to take on a bet with a friend that he couldn't summon some insanely horrible tentacle horror from the dimensions beyond human reach, it should be noted that the challenge was issued during the consumption of large quantities of alcohol, and carried out after the consumption of even more alcohol. The fanboy learned two tings that night... Never use the AD&D rulebook as a necronomicon, and second, don't try to invoke any supernatural creatures when you pissed out of your mind.
He actually managed to summon something, the spirit of Kalewynn. No one knows how he did it, but despite having his body destroyed, disintegrated, Kalewynn's spirit refused to die and hung at the edge of the shadowlands...unfortunately, his sanity went goodbye along with his body and almost all that remained of him was pure raging fury. Sometimes when some stupid cultist tried to summon something, they sometimes opened a door for Kalewynn to get through, get inside the practitioner's head, and ravage his mind before returning to the deadlands...
This time however something happened that allowed the fanboy to save his mind (not that there was that much of it to begin with), when Kalewynn's spirit got into this guy's head he was momentarily dazed by the mental images of naked Sarah Michelle Gellar having hot lesbian sex, and then it got as drunk as his host, Kalewynn instinctively tried to rip and tear everything but he only succeeded in rolling himself up inside the rags that were the fanboy's mind.
Since then the two have fused into one being, predictably though the result of this union is a particularly deranged individual that spend most of his time between states of total and complete insanity some very scarce lucid moments in which one of his personalities take over. When it's the human, he just curls up in a corner and starts rocking back and forth while humming softly to himself like a guy in a padded room. What was Kalewynn on the other hand has regained some level of composture since the mind-meld and now has some degree of self-control and a few memories. When it's the old Kalewynn, after he deals with the disgust of the human body he's in, boy are we in trouble.
He also suffers from severe migraines, which can only be remedied through the large consumptions of alcohol.
The Most notorious power Kalewynn has is the ability to shape shift into a fully-grown dragon, large, fire breathing and scaly. He's also capable of performing quite a bit of magic, which he can use even while in insane mode, since he seems to have tapped it at some sort of subconscious level. The main problem is that because the dragon form is an adopted form and far too powerful for his own good, when he stays for too long in it he suffers horrible pains. Just being in full dragon form and doing nothing exhausts him after an hour, if he uses all his power at power, he can't really put up with it for more than 10-15 minutes, but believe me, he's something that can make even Stardarke get a run for his money.
It was only normal that he ended in the Funky Horror being some kind of insanity black hole toward which reality-warping individuals gravitate to.
Sometimes it has happened that the fanboy's mind has kicked in the middle of the transformation, changing the shapeshift to something utterly different from a dragon. When such things happen, Kalewynn is aware that something has gone terribly wrong, but the fanboy is usually having so much fan that he can't really put his claw on what it is.