Skeletal horse mounts

Skeletal horse mounts are almost exclusively Horde only mounts.

Factional mounts: Apprentice
These mounts give a 60% speed increase on land. You can purchase these mounts from in Brill in Tirisfal Glades so long as your character has riding skill of 75 (obtainable at level 20). If you are playing as any race other than an Undead, you will also need to have reputation with The Undercity.

Factional mounts: Journeyman
These mounts give a 100% speed increase on land. You can purchase these mounts from in Brill in Tirisfal Glades so long as your character has riding skill of 150 (obtainable at level 40), and are restricted similarly to the apprentice mounts above.

PvP Skeletal horses
The Red Skeletal Warhorse is available from in Hall of Legends for Honor points. You do not need to have exalted reputation with The Undercity to purchase it.

Argent Tournament
These following Skeletal horses can be purchased from the Argent Tournament. You must have completed or be an undead to gain access to this quartermaster.

Skeletal horses as loot
The only example of a dropped Skeletal Horse is Rivendare's Deathcharger, dropped by Baron Rivendare in Stratholme. While obtainable by both factions, it is the only skeletal horse available to the alliance.