Frosthearted Steed

The Frosthearted Steed is a level N flying mount.

Source
The mount can be obtained from the Emissary of the Damned in Torchkeep upon hitting Exalted reputation with the Cult of the Damned. When you buy the mount, you can no longer obtain the Steadfast Scarlet Charger (the Scarlet Crusade reputation mount) or the Elder Smoldertail Kobra (freelancer mount).

Mount Journal
''Conjured by the best spellcasters of the Cult of the Damned, only a handful of these mounts exist. Let your enemies know the fury of the Damned as you ride into battle on this fearsome steed... and don't forget to hug Kel'thuzad, he needs it.''

Special Abilities
If you die and this horse was the last mount you used, it has a chance to spawn in the Shadowlands and follow you. Most of the time it is unmountable, but sometimes you can right-click it and ride on it to the location of your body (you get automatically dismounted upon reviving yourself). Its tattoos glow vibrantly whilst in the Shadowlands.

Tattoo Colors
The steed's tattoos (those stripes that make it look like a frozen zebra) glow and their color can be changed using these two items:

Time-forgotten Spellstone
Main article: Time-forgotten Spellstone

When this item is used, the tattoos change color to your class color (Death Knights get red, Demon Hunters purple...).

Chromatic Dragonbone Shard
Main article: Chromatic Dragonbone Shard

This item causes the tattoos to change colors randomly upon entering a different main zone (subzones don't count). The colors range from light shades (even from white) to dark shades of colors (it is possible to get black, too.)

Trivia

 * Its wings are spectral and they change their colors along with the tattoos.