Reins of the Quantum Courser is a Very Rare drop from the final boss of the Dawn of the Infinite mega-dungeon. It teaches you a mount from the past, and we’re looking at the mounts that have been confirmed so far.
LeystTv so far confirmed the following mounts learned fromĀ Reins of the Quantum Courser:
Midnight’s Eternal Reins from Legion Karazhan;
Cartel Master’s Gearglider from Tazavesh;
Reins of the Infinite Timereaver from Timewalking Dungeons;
Apparently, Marrowfang’s Reins can also drop.
Although it hasn’t been confirmed, it appears the mount teaches Mythic Dungeon mounts.