Warforged Nightmare

The Warforged Nightmare is a product of molten metal, raw fire and fevered dreams. This terrifying steed was crafted from cold, hardened steel and vengeful spirits by grandmaster smiths, and gives the owner the ability to place a Nightmarish Hitching Post. This mysterious artifact has the power to summon a Warforged Nightmare for every member of your war party strong enough to handle the reins and worthy enough to be given the honor. The next time you rally your comrades to mount up and earn their keep, charging into battle astride this mount will embolden your friends, send your foes slinking for cover, and unleash unbridled chaos upon your enemies!

Source
This item is available for purchase from the shop or the In-Game Store for $30 or €30. It was released on June 11, 2014.

Mount Journal
A nightmarish steed of hardened steel and vengeful spirits, this companion will follow you to the depths of the Firelands and back without complaint.

You and your friends can ride boldly into battle on this metal masterpiece.
 * In-Game Store

Form a Nightmarish Posse - ''Charge into battle astride a Warforged Nightmare, unleashing unbridled chaos upon your enemies! Ownership of this terrifying steed, crafted from cold steel and vengeful spirits by grandmaster smiths, allows you to place a Nightmarish Hitching Post. This mysterious artifact has the power to summon a Warforged Nightmare for every member of your war party strong enough to handle the reins and worthy enough to be given the honor.''
 * Blizzard Shop

Notes and trivia

 * Players who own this mount can place a Hitching Post every three minutes, which is only visible to party members. Interacting with it will apply the Nightmarish Reins buff to the user's mount, with the cast time of a regular mount.
 * It was released on June 11, 2014, and was the eighth mount to join the in-game shop.
 * This mount was inspired from the Bridle of the Ironbound Wraithcharger's original concept. During Mists of Pandaria, the latter was supposed to come from a Pet Store item known as the Iron Hitching Post. It would have allowed party and raid members to make their mount appear as an "Iron Warhorse" for a limited amount of time. However, unlike the cosmetic helmets announced in the same blog post, the Iron Hitching Post was never released. The idea was later incorporated into the Warforged Nightmare mount with the Nightmarish Hitching Post.