The Theophanist, or "I get to summon the Abrahamic God as a 10th-level ability"
Clarification: This fluff text is something I made up, not from the book.
The Case of Sir Percival of Yorkshire, Master Theurge, 1100 AD:
The ritual was in place. The summoning circle, painstakingly crafted in 6 hours, theorized for years, gave off a shining white glow. Sir Percival managed to do what the Catholic Church never dreamed of, for they condemned his theurgic ilk. He once dreamed of ruling the British Isles during his apprenticeship before learning of the shortsightedness of this goal. Holy Cross in hand firmly placed upon his spellbook, Sir Percival of Yorkshire was ready to assume an even greater mantle: the King of Heaven.
"Lord Almighty, Jesus of Nazareth, I summon thee! Place your power onto me!!"
The bright light arced out of the circle and enveloped him.
Percival gasped. "I see... beautiful visions of Heaven! Streams of pure water and golden gates, far as the eye can see! A world without suffering, of eternal bliss, all within my grasp!"
What he saw next was too glorious to describe in words. "It's God, the Creator Himself! I command ye to do my bidding!"
God's Word was revealed to Percival, in such eloquent terms that the theurge was shaken to the core of his being. "You can't rob me of all this power," he shouted, "Decades of toil, dedication! Do you know how many people I had to sacrifice to reach this point?!"
Visions of hell, of fiery pits and deformed sinners, their ugly forms borne of torture. "This is what awaits the Theurge who rebels against God's Will!" To his horror, Percival realized that this pronouncement came from his own lips.
"You can't make me choose!"
The Continuing Case of Sir Percival of Yorkshire, former Theurge turned Mendicant, 1105 AD:
Percival has never felt so free in his life. He gave up his castle, his inheritance, even his noble title, all to make his subjects happy. The once grand estate of Yorkshire now belongs to everyone. Although he had good intentions, freely giving all the riches and grain to the peasantry was not wise in hindsight now that even the village mayors are fighting bloody battles over the Royal Pillowcases.
Lady Eloise still clings to her husband. At first she enjoyed his more noble demeanor and loss of arrogance, but she grew to miss what he once was. "It was as though he were a different person!" she thought. She cursed the foul art of magic under her breath, of how it turned her beloved into a complete stranger.
The Medieval Player's Manual by Green Ronin is part of the Mythic Vista series, a collection of d20 campaign settings in real-world historical locations. The MPM takes place in Medieval Britain and north France, circa 1067-1150 AD.
In order to get a better "Medieval" feel, several core classes were omitted and replaced with more setting-appropriate material. The magic system works a little differently as well.
Magic in general is not sinful in and of itself, but it can be put to sinful ends. Theurgy is one of the three kinds of magic in the setting, and the only form that is inherently sinful. Theurges draw upon the power of spirits through scholarly rituals and methods. Basically, they use the d20 magic system, but the more powerful magic requires time and material components.
The Theophanist prestige class is a theurge who plans to summon the most powerful spirit ever so that he can enforce his will upon the world. The prestige class' modus operandi is dedicated to learning the sole class feature at its final 10th level: Beatific Vision, or "Summon God" in laymen's terms. Trolling potential from flavor text alone: 9,000+.
Given that we're talking about a 10th level Prestige Class that loses two levels worth of casting, and we get to summon the Abrahamic "beyond human limits" God, nothing could possibly go wrong!
Reach 10th level, and something like the above story happens...
If the theophanist accepts God, he changes to Good alignment, and loses all levels of Theurge and Theophanist. Genuine loss: all feats, skill points, hit points, saving throws, all of it, lost. In compensation, he gains one level of the Saint class. This means that a Theurge/Theophanist can revert to 1st level.
Additionally, the character is no longer capable of sinning, or even having sinful thoughts. If the player tries to make his character sin, then the DM declares that the PC does not commit the action. But to be free of sin is to not be human. Your character can't even experience emotions such as anger, greed, or lust! Now your character can't screw the barmaid and he can't go on adventures for money (unless this money would be given to charitable causes). The prestige class just trolled you right back!
But the player can reverse-troll the situation: If the theophanist refuses God's Will, your character keeps all of his abilities, but he is truly and irrevocably damned. He changes to Evil alignment; he can still commit good actions, but they will never be of good intent.
Regardless of the choice, the character gains the Resurrection Body Charism. He or she is now immune to effects of the physical world. He is immune to poison, disease, all non-magical damage and effects. He can walk through all manner physical objects, flawlessly teleport anywhere in an instant without having to know the location, and can fly. All Charisms are extraordinary abilities, and thus cannot be dispelled by magic. He can still interact with the physical world if he chooses to, and can be selective as to what aspects of it affect him.
Any sensible player should know better than to think that a spell in a Medieval setting meant to command God Himself comes with no strings attached. This is why it's the perfect troll class. It's trolling the players who don't want to be Evil because it's forcing them to gimp their character (both for losing two spellcasting levels and the 10th level ability); players who don't care about damnation or alignment get the ability to troll the Dungeon Master forevermore. Since the Evil Theurge accepted his sinful nature and is incapable of acting with good intent, he can screw up almost any conceivable adventure plot with the "transcendent, unaffected by crude matter" abilities. And he can fall on the "I'm role-playing excuse" whenever he acts like a disruptive psycho.
tl;dr: Accept God, lose 15+ levels in every sense of the word. Lose the ability to sin or even have sinful thoughts, which significantly changes human nature. Reject God, keep all of your powers but become Evil with a capital E.
Get the ability to say "screw you!" to all non-magical damage, get to teleport anywhere, go through all manner of solid material. This is an extraordinary ability, meaning that it can't be dispelled by magic.
