Sourcery recap

Rincewind, the Disc's most useless wizard, is swept up when sourcery returns to the world. The dying wizard Ipslore binds his vengeful will into a staff and gives it to his infant son Coin, a sourcerer whose raw magic outclasses ordinary wizardry. Grown, Coin takes over Unseen University and, driven by his father, incites the wizards to abandon restraint, raise war, and remake the world, which thins reality and invites the predatory Things from the Dungeon Dimensions. Rincewind, entrusted with the sentient Archchancellor's hat, flees with Cohen the Barbarian's warrior daughter Conina, the would-be hero Nijel, the wealthy Seriph Creosote, and the Luggage. As catastrophe nears, Coin realizes his staff has been controlling him and destroys it, breaking free of Ipslore. Rincewind holds off the invading creatures by walking into the Dungeon Dimensions himself. The world is saved, Coin leaves to build a private world of his own, and Rincewind is left trapped outside reality, his rescue still to come.

Rincewind is an inept wizard of Ankh-Morpork's Unseen University who can perform almost no magic, having had one powerful spell from the Octavo lodged in his mind years earlier. In earlier adventures he served as guide to the tourist Twoflower and survived a string of catastrophes largely by running away, accompanied by the Luggage, a devoted and dangerous walking chest of sapient pearwood. He remains attached to the University, and to his own survival above all else.

The dying, disgraced wizard Ipslore refuses to give up his soul and instead binds his will into a staff, handing it to his newborn eighth son, Coin, a sourcerer, a source of raw new magic of a kind not seen for centuries. Years later Coin comes to Unseen University in Ankh-Morpork and, driven by his father's staff, effortlessly dominates the wizards, reawakening their ambition and reviving high magic across the Disc. The inept Rincewind, who wants only peace, ends up entrusted with the Archchancellor's hat, a repository of wizardly wisdom that begs to be carried out of the sourcerer's reach. With the warrior-hairdresser Conina, daughter of Cohen the Barbarian, and the ever-present Luggage, he flees the city.

As sourcery spreads, the wizards abandon their old restraint, raising towers and preparing to remake the world with unlimited magic. Rincewind and Conina carry the hat toward Klatch, and their path leads to Al Khali and the court of the Seriph Creosote, a wealthy, poetry-loving ruler. They fall in with Nijel, a skinny young man trying to teach himself to be a barbarian hero from a book. The struggle over the Archchancellor's hat, and over what should be done about Coin, entangles them all, while back at the University the sourcerer's power keeps rising and the balance that once kept magic in check begins to fail.

The world tips toward catastrophe. Under Coin's influence the wizards wage a war of magic, and the sheer weight of power being used thins the walls of reality, drawing the attention of the Things from the Dungeon Dimensions, hungry entities that wait outside the world for a way in. The gods themselves are stirred toward conflict. Rincewind, Conina, Nijel, and Creosote make their way back toward the heart of the crisis at Unseen University, while it grows clear that Coin is not acting freely but is the instrument of his dead father's vengeance, carried in the staff he cannot bring himself to put down.

At the climax the excess of sourcery has torn openings for the Dungeon Dimension creatures, and the world is on the edge of being overrun. Coin comes to understand that his father's will, lodged in the staff, has been using him, and he finally breaks free by destroying it. Rincewind confronts the invading Things directly, stepping into the Dungeon Dimensions armed with little more than a half-brick in a sock to hold them back long enough for the breach to be closed. The University and the world are saved, and high magic subsides. Coin, too powerful to live safely among ordinary people, uses his power one last time to make a world of his own and departs. Rincewind is left stranded in the Dungeon Dimensions, alive but cut off from the world, having given up his escape to save everyone else; the Luggage sets out to find him.

Sourcery ends with the world pulled back from destruction at Rincewind's expense. The unchecked use of sourcery had worn the walls of reality thin enough for the Things from the Dungeon Dimensions to begin breaking through. Coin, the boy sourcerer, at last recognizes that the staff he carries holds the will of his dead father Ipslore and has been driving everything he has done; he frees himself by destroying it. To stop the invading creatures, Rincewind steps through into the Dungeon Dimensions to fight a holding action, armed with a half-brick in a sock, buying the time needed to seal the breach. Unseen University and the Disc are saved, and the flood of high magic recedes. Coin, whose power makes him too dangerous to remain among ordinary people, uses it one last time to create a separate world for himself and departs. Rincewind, however, is left behind, stranded in the Dungeon Dimensions beyond the edge of reality; he is alive but cut off from the world, and his return is left for a later book, while the Luggage sets off to look for him.