Players who accomplish the Glory of the Dream Raider achievement in Patch 10.2 will obtain the Reins of the Shadow Dusk Dreamsaber mount.
Glory of the Dream Raider is composed of 9 accomplishments (1 per boss) that you must fulfill in Amirdrassil.
Reins of the Shadow Dusk Dreamsaber
Enveloped within the shadows of twilight, they glide through the darkness and prey upon their targets. Few have witnessed them, and only as they retreat back into the shadows with their meal in mouth.