Undead dragon mounts

Undead dragon mounts are flying mounts first added to World of Warcraft with Wrath of the Lich King.

Achievement

 * Reins of the Bloodbathed Frostbrood Vanquisher is a reward from Glory of the Icecrown Raider (10 player).
 * Reins of the Icebound Frostbrood Vanquisher is a reward from Glory of the Icecrown Raider (25 player).

Arena
Frost wyrms were rewarded for the Wrath of the Lich King arena seasons at level 80.

Drop

 * Smoldering Ember Wyrm drops from Nightbane in Return to Karazhan.

Quest

 * Deathlord's Vilebrood Vanquisher is a reward from the death knight quest The Lost Glacier (quest). It changes appearances when you switch specializations