Blue water pixie does not exist?

I’ve now 13 of every other pixie, trying to get just a single blue one. It seems quite unbalanced, or impossible that I’ve never even seen a blue pixie in the woods

Try going to the water dungeon in chapter 3 of the online missions. Seapixies appear there sometimes.

^ Right.

I acquired a Seapixie just a while ago. I found it in the Water Valley dungeon in Chapter 3 of the online story missions.