So, after I completed the quest and turned it in Oribos, the current timewalking vendor (this week is cata-> vendor is in Stormwind or Orgrimmar) will allow you to buy the other 3 mounts.
However, as of the current build, you can see them ONLY on the character you have completed the 5xWeeks quest.
Each of them cost 5000 badges, so 15000 in total.
Edit: As of WOD event of the week of 14th of January - all mounts are available on all your account.
Quest
Ta'readon's Mount Voucher
A World of Warcraft quest in Oribos. Facts and objectives from the current retail game data.
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I already know what char finished this quest, but all my chars say false, on Tbc week, so i cant buy the mounts.
once you've completed the achievement and gotten your "free" mount, the 3 others become available from vendor Kiatke (in Orgrimmar this week, I presume Stormwind for the alliance) for 5000 time walking badges.
Quest facts
The client quest POI data records no map location for this quest, so no map is shown.
Check whether you have already completed this quest
in-game: /run print(C_QuestLog.IsQuestFlaggedCompleted(92857))
Description
This token bears the seal of Overseer Ta'readon in Oribos. They would be interested in seeing this.
Community notes from Wowhead · 17 comments
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“Teaches you how to summon this mount.”
“Teaches you how to summon this mount.”
“Teaches you how to summon this mount.”
“Teaches you how to summon this mount.”
Item facts are the current retail client’s (ItemSparse); the specialisations for a pick-one item are the ones the Blizzard quest API lists; faction and currency text is the client’s own. Lowest listed price = the US commodity auction house now.