From the Chronicles of Amber:

Avalon was Corwin's favorite Shadow in his youth. He spent a great deal of time there before his exile, so much that Avalon may well have begun casting Shadows of its own.

** Minor Spoilers if you haven't read The Guns of Avalon and Nine Princes in Amber **

After his escape from the dungeons of Castle Amber, Corwin sought to return to Avalon, where he could acquire a substance that ignites like gunpowder if brought back to Amber (centuries before, Corwin had learned that gunpowder does not ignite in Amber). Upon arriving at Avalon, he discovers that so much time has passed there that he is remembered as an evil sorceror rather than benevolent ruler. His brother Benedict, long absent from Amber, now rules Avalon as Protector. He warns Corwin that while he welcomes a peaceful visit, he will not tolerate the land being used as a staging ground for Corwin to raise an army to take the throne of Amber.