Knights of Tezoth

If you enslave a dragonid, can it be used as a mount? 🤔

No.

Technically, during the "dark screen" you can.

In that regard, yes.

In the capital, will it be hard to get? Where is it easiest?

In Lunia it's the easiest. In the capital, the simplest way is in the context of "please my queen, I really need a wyvern, get one for me pls, it will help me be even more useful to you than before 🥺".