There are four mounts unlocked by renown in each Covenant
One at Renown 23 (Costs 5000)
One at Renown 39 (Free)
One at Renown 45 (Free)
One at Renown 70 (Costs 7500)
Another factor that makes thes mounts easy to collect is the addition of Broker Mark of Distinction in Patch 9.1.5. With this item, you can instantly get to Renown 40 in all Covenants, as long as you’ve reached 80 in your main one. With that, you can instantly unlock the mounts from Renown 23 and 39 from your other Covenants after you max one of them, plus leaving you extremely close to the Renown 45 one.
None the Wiser Guild 