Spoiler alert: This post is part of an in-depth discussion of The Hand of Oberon by Roger Zelazny, which will inevitably reveal key plot points. I recommend you support your local bookseller or public library, and read the book first.
Corwin paid a visit to the mad Dworkin, architect of the Pattern that is the source of the Amberites' power—and, as he learned, his grandfather. Dworkin wanted to destroy the primal Pattern, which was marred with the blood of Martin (the son of Corwin's brother Random), and remake it. But Corwin, posing as his father Oberon, wanted to try and repair the damage. As Dworkin's madness came over him and he transformed into a clawed being, Corwin escaped using a random Trump from his desk—only to find himself in the Courts of Chaos.