The main source of information for the events leading up to the Cataclysm is the first post of Epic Quest: The Sequel, but some did happen before those events. The Baker, after being slain by Abyss, quickly reincarnated in quasi-angelic form and sacrificed his Ban-Hammer to destroy the Cornchips. After this, though, Abyss recovered all that he had lost (minus the Cornchips), nearly slew The B-Team (EQ:13:2).
It was then that he grew immeasurably in power, causing the universe itself to tear apart. Planets crumbled, stars went Super Nova, and whole galaxies were suddenly snuffed out. Some reality still remained, and the B-Team fled in their Yem-Shui Mk. V. For three years they practiced their final assault to destroy Abyss, which they knew would have to be so powerful that it would destroy the entirety of what remained of the universe.
Without warning, Abyss confronted them again. He set up an arena, in which each member of the team would be spared their lives if they could even wound him. He was about to kill all of them with a whim, when the team retaliated with their ultimate plan.
The plan involved great and laudable deeds, the likes of which not even they had displayed before. (Good read, good read; (EQ2:1:1).) Their final move involved morphing an Original Flavor Blueberry ChozoMufins with a Light Glazing and Just a Hint of Lemon, Guitar Hero's guitars, and Jacen's lightsaber into a recreation of the Ban-Hammer. This then detonated with irresistible power, destroying the entire universe.
Soon after, stars and planets reappeared. The Human race also revived on Neo-Earth; in fact, the planet itself was in almost precisely the same location, and even had similar continents. The likelihood of this happening (and the spontaneous generation theory in general) is impossible, so it is said that the power of God was present in the explosion, coupled with the B-Team's last will. The Neo-Universe rapidly reformed out of nothing, and almost precisely as it was before.
The B-Team had managed to leave behind The Book of Epic somehow, and many had even survived the Cataclysm through various means.