Initially, I thought the Indrik mount was available for a limited time. I had picked up the evolution lore paper at the Impresario, but it still didn’t click.
If you hit F1 in-game, you’ll find more evolution info about the mount under the Event section under Nascent Indrik Creation and Nascent Indrik Evolution. It appears that event tickets will continue into events next year and after creating the original Nascent Indrik, you’ll be able to evolve it 4 times into the Dawnwood -> Luminous -> Onyx - > Pure-Snow using special berries bought from the Impresario in later events.
You’ll need another Nascent Indrik if you want to evolve another and keep one of each evolution. If my math is correct, we’ll need 5 of each feather. Each evolution requires buying special berries from the Impresario with event tickets. Berries will be introduced in 2019 after the initial Indriks become available with the New Life Festival.
Find more info in-game in the F1 Help Menu (Events).
Here are a couple more info links: