Spoiler alert: This post is part of an in-depth discussion of Sign of the Unicorn by Roger Zelazny, which will inevitably reveal key plot points. I recommend reading the book first. It's short, I promise.
To rest and to recover from the stab wound he has kept secret from his family, accompanied by Random and Ganelon, Corwin ascended Kolvir to visit the floating city of Tir-na Nog'th, which appears above the mountain only by the light of the full moon. In Tir-na Nog'th, he experienced several visions. The last of these, seemingly of the future, was of Dara on the throne of Amber with Benedict at her side. He has a mechanical arm, replacing the one he lost fighting hellmaidens in Avalon. She proclaimed herself the rightful queen of Amber and said Corwin had been dead for centuries. When Corwin challenged her, Benedict drew on him with his own sword, and they fought. But as day broke, Tir-na Nog'th began to fade, and Random reached out to him via Trump to draw him back.
In Tir-na Nog'th, the apparitions and Corwin were immaterial to each other. However, safely back on solid ground, Corwin learns that Benedict's metal arm is nonetheless solid enough to have grabbed him by the shoulder and be drawn back to Amber. Corwin, Ganelon, and Random have a meal, and they discuss the Amberites' complicated family tree and the line of succession to the throne.