I've been playing D&D for about 20 years, this story occurred back in the early days of college and has shaped every game I've run since.
In this game, it was summer and myself and some friends had gotten together for what we had intended to be a light-hearted and mostly jokey D&D 3.5 campaign. What we got instead was what would become a very intense campaign that most of us to this day laud as one of the greatest campaigns we'd ever played. The premise was deceptively simple, each of our characters was going to be a Dragon. We could pick any kind of dragon to play, we would all be granted the ability Change Shape so we could masquerade as humans in the world of Faerun. We were meant to be an advance scouting party, determining if it was the time for Dragons to return en-masse and take over the world. We had an extremely diverse group, ranging nearly all the alignments and various flavors of dragon. We also got to take character levels on top of our DM's homebrewed system for spending money to forcibly increase our age categories, so we knew from the start that this game was going to be really overpowered.
I decided to lean into this as hard as possible. I did some research and found that it was generally accepted at the time that one of the craziest things you could do was play a Tome Dragon, a dragon from the Dragon Magazine that had exceptional casting capabilities, and give it the Spell-Hoarding Psychoses, another Dragon Magazine addition. This made for an extremely powerful spellcaster with a literal psychotic focus on collecting arcane knowledge. For class levels, I decided to pursue Artificer, as this would let me do more than just wizard things, and would provide an easy source of magic items to the party. I ended up dubbing this creation "Vehafor Arcaniss", which meant "Craft Magic". This creation would eventually be dubbed "Hafer" by the party, and would the source of much consternation for my players in future campaigns.
Even in the midst of playing this definitively power-gamer character, I couldn't help but throw in some roleplay. I leaned heavily on his psychotic nature for easy roleplay fuel, and furthermore I gave him a single-minded drive. He wanted to pursue the source of all magic, True Magic as I had dubbed it. Neither Arcane nor Divine, it simply was. Credit to my DM, he definitely let me pursue something that probably didn't exist. Our campaign lasted throughout msot of the summer, and we rapidly scaled in power, both in class levels and dragon age categories as we used our draconic might to overpower most of our foes. We also got to experience some incredible roleplay as we had to navigate different political courts all while hiding our true natures. We also ended up forming an official adventuring company, and made a name for ourselves as efficient, if somewhat brutal, adventurers. There are so many moments from this campaign that deserve their own stories, but right now, we're here to talk about Hafer.
As we grew near what would become the end of the campaign, our DM worked to try and tie up several of our personal story hooks and goals, my own included. This came when we encountered a Titan who had access to "True Magic". We managed to talk him down from combat and I entered into an extensive bartering session. He wanted my entire collection of spells and magic items in exchange for the knowledge. This battled against my psychoses, and I gave it up to a throw of the dice, would my insanity prevent me from giving up, a low roll, or would I seek out my ultimate goal and rebuild, a high roll. Natural 20. I gave up my hoard of spells, scrolls, magic items and assorted goods to the titan in exchange for the knowledge.
My DM then informed me that I had lost all of my spell slots from any class or source. Instead, I was now using a modified spell point system, where any spell slot I had gave me a certain number of spell points, which I could spend to cast a spell from any spell I had access to. More importantly, they were gained or spent at simple ratio. Spell level squared, so a first level gave me 1 and cost me 1 point. A 9th level gained me 81, and cost me 81. He specifically stated that I could spend these points in any number, as long as I followed that ratio, even casting beyond 9th level spells. One final crucial detail would come into play. In this campaign, the DM had ruled early on that we, as Dragons, could "stack" metamagic effects. Usually this was used for Empower, letting us repeatedly boost lower level spells to much higher effect. The Titan, after granting me the knowledge and me handing over all my personal effects, tried to kill me, suddenly realizing that I may have become more powerful than he was anticipating.
In a moment of sheer madness, or brilliance, depending on who you ask, I dumped all of my power into a single spell. Magic Missile. Empowered as much as possible. When the math shook out, the spell did something to the effect of a billion points of damage. As everyone around the table, including myself, sat in pure shock at what I had just done, the DM came out of his trance and acted quickly. My single spell utterly destroyed the Titan, but it also tore a hole in the fabric of reality, and in the fabric of the Weave, the source of magic on Faerun. The Goddess of Magic, Mystra, appeared in that moment to destroy the source of the rent. However, the DM made a second call as Mystra had appeared. Hafer, in his moment of pure calamity, had done something that shouldn't be possible, and was granted a single Divine Rank. My shock increased as the DM announced this, because with my knowledge of the system I had a moment of pure understanding. Upon gaining a divine rank, deities would gain a Divine Salient Ability, only one of which mattered to me in that moment. Arcane Mastery. This ability would mean that Hafer would essentially gain knowledge of every wizard spell that ever had, did, or ever would exist, and could create new ones at the speed of thought.
Hafer, suddenly overflowing with knowledge, couldn't react as Mystra shunted him from the plane, forever banning him from returning to the Prime Material Plane of Faerun. This mattered little to him, for in that moment, his Psychoses was suddenly satisfied. His desire to know everything Arcane had been realized. The table sat in silence as I explained this to them, and what followed was a rapid debate. Did Hafer simply die, having realized his life's ambition? Or did his Psychoses now twist, compelling him to not simply KNOW all, but to RECORD all? I ultimately settled on the latter. Deciding that his Spell-Hoarding Psychoses, coupled with his now limitless knowledge of Arcane spells, would compel him to forever record the spells, every spell that had ever been created, and every new spell that his incredible intellect could conceive of, even ones that should not be possible.
And so, Hafer now sits adrift in the cosmos, in his own personal dimension, an endless library of magical knowledge. Forever compelled to keep writing, his own insanity leaking into other dimensions as he passes them by, leaving impressions of himself in his wake. The great glowing dragon, with an massive tome sat before him, ever-writing, ever-thinking, ever-smiling. Woe to those adventurers who might come across him, for they may leave with great riches, or be burdened with horrible curses, all at the whims of a truly Mad God.