Interestingly enough, I wonder if the 4 feathers double as a means to tease what you can evolve your Nascent Indrik into!
Emerald Indrik Feather (Witches Festival): Dawnwood Indrik (Green Indrik)
Gilded Indrik Feather (Clockwork City Anniverary Event): Luminous Indrik (Gold Indrik)
Onyx Indrik Feather (Undaunted Event): Onyx Indrik (Black Indrik)
Opaline Indrik Feather (New Life Festival: Pure-Snow Indrik (White Indrik)
Most of the first set of "Berries" (the items used to transform you Indrik into a new form) have been data-mined as well. 3 out of 4 of the "Dawnwood" berries can be found in the game's data at this point.