Fair enough, I'll probably be looking into adding thematic stuff from it into his design for tier 3 then! (Since I was going more for the "switch into a closely-related type" thing than powered-up fog form.)

In that case, follow-up question: what kinds of alternate monsters would be permissible for a faerie's tier 3? As I mentioned initially, a lot of faeries and faerie-like creatures in lore would fall a little close to other monster categories (e.g. dryads to nymphs, dwarfs and gnomes to goblins, undine/selkie to mer, cat sith and cu sith to weres, water horse to kelpie, etc.) for me to be entirely clear on what would be allowed there.