From WoWWiki

Source

This item is a rare drop from Headless Horseman. The horseman is found in the graveyard wing of Scarlet Monastery during the Hallow's End seasonal event.

Notes

It is BoU, and has a 14 day duration from when first used.

This item is dropped by the Headless Horseman who is summonable at the Pumpkin Shrine located in the middle of the Forlorn Cloister, in the graveyard wing of Scarlet Monastery.

You can summon him if someone in your party or raid has the  [70] Call the Headless Horseman quest available from the Pumpkin Shrine. The quest counts toward the daily quest limit. You will receive a [Dreary Candle] with the quest, right-clicking the Loosely Turned Soil — behind the Pumpkin Shrine — will start the scripted event.

The item description indicates that it is one-use, but this is not correct.

External links

Neutral Mounts
Class Based	Death Knight: Deathcharger Paladin: Warhorse • Charger Warlock: Felsteed • Dreadsteed
Pre-Burning Crusade Drop Mounts	[Deathcharger's Reins] • [Swift Zulian Tiger] • [Swift Razzashi Raptor] •
Burning Crusade Drop Mounts	[Ashes of Al'ar] • [Fiery Warhorse's Reins] • [Reins of the Raven Lord] • [Amani War Bear] • [Swift White Hawkstrider] •
Faction Mounts	Riding Talbuk • War Talbuk • [Cenarion War Hippogryph] • Nether ray • Netherwing drake mounts
Crafted Mounts	[Flying Machine Control] • [Turbo-Charged Flying Machine Control]
Holiday Mounts	[Fresh Holly] • [Preserved Holly] • [Brewfest Ram] • [Swift Brewfest Ram] • [Magic Broom] • [Swift Magic Broom] • [Flying Broom] • [Swift Flying Broom] • [Rickety Magic Broom]
TCG Mounts	[Riding Turtle] • [Reins of the Spectral Tiger] • [Reins of the Swift Spectral Tiger] • [X-51 Nether-Rocket] • [X-51 Nether-Rocket X-TREME]
Other Mounts	Qiraji battle tank mounts • [Black Qiraji Battle Tank] • [Dark War Talbuk] • [Dark Riding Talbuk]