Grayswandir
Grayswandir is Corwin's sword, also known as the Night Blade; its twin is Brand's Werewindle, the Day Sword. Both Grayswandir and Werewindle are inscribed with portions of the Pattern of Amber; this makes them particularly effective against creatures of Chaos. In addition, Grayswandir has one magical property that makes it particularly useful: Corwin can call it by creating a Shadow where he wills it to exist. Unlike a normal blade, Grayswandir can also harm apparitions, and allows Corwin to speak to the shades in Tir-na Nog'th.
In the Amber short story "Hall of Mirrors", Corwin revealed that Grayswandir and Werewindle were transformed spikards. Spikards are rings of power that existed before Amber, and possibly even Chaos, were created; they allow the bearer to tap into the raw power of the Amber universe. For reasons unknown neither Corwin nor Brand used their powers during the Patternfall War.
The name Grayswandir echoes that of Graywand, the longsword of Fafhrd in Fritz Leiber's tales of Fafhrd and the Gray Mouser, a likeness that may or may not be coincidental. Unlike Grayswandir, Graywand has no magical properties, or even identity as a unique artifact; rather, Fafhrd bestows this name on any longsword he happens to possess and use.
Read more about this topic: Corwin Of Amber