Long-Forgotten Hippogryph

You are the only one that remembered.

Riding Requirements:

This mount is available to all eligible characters on your account.
Level 10
Apprentice Riding (ground)
Expert Riding (flying)

Source 1:

Ephemeral Crystal puzzle in Azsuna, Broken Isles.

Source 2:

Coming in Patch 11.2.5

Sold by Hemet Nesingwary XVII in Infinite Bazaar, Dalaran (Legion Remix).
Cost: 20 000

Notes:

This beautiful older hippogryph may be obtained after a small adventure. The Wowhead community worked out the method of obtaining it - which involves being the first to locate 5 randomly-spawning purple Ephemeral Crystals in Azsuna and clicking on them within an eight-hour period, without dying. For maps and directions to all the crystals, see Warcraft Secrets' guide, or check out Wowhead's comments.