Thanks a lot for the summary Aaz and Puela!
Absolutely fantastic episode.
The diversity of denizens from this Island and the richness of the deep folkloric overtones shown in this episode are a tremendous joy to see and feel.
I also enjoyed seeing Serpico "courted" and taken by the wind folk. In the same page there's this wide big panel of Farnese and Casca caught by the plethora of astral creatures in this sort of joyous march. I'm reminded of Miura's take on the Garden of Earthly Delights on episode 306, this time presenting what feels like a much more lighthearted and friendly march here. There's even an elf that resembles Irvine with the bycocket-esque hat and the musical instrument, some form of violin, so can't say she's missing a bow either!!

Schierke's guess about the boy was based on very general information though, so it wasn't a specific indication of what kind of avatar the Elf ...Leader... can take. Especially since her assumption about the boy is mistaken.
Yup, it's just the contemplation of the idea simply being raised by Schierke, added to the concept brought up by Ivalera and being somewhat illustrated by Isma's case, even though Isma may not be a proper astral creature or elf, and had been at the time our only example (although Ivalera does say in a relatively including manner that elves, spirits and other kins have a true or secret name that governs their true form). The idea just felt plausible and appealing to me, both in-universe due to these related enough elements and based on fairy-folk tales across the world.
As I was reading yesterday in one encyclopedia, fairy tales are ridden by all sorts of elf-folk that come in the most diverse sizes and shapes, as well as often enough the capability to shapeshift.
I find it really crafty from Miura's part how he's able to keep firmly rooted to a lot of the source inspiration while not feeling necessarily limited by it. A lot of the fantasy content feels very close to a lot of folk-tale sources, yet in some ways it also feels like its own thing. My impression of course.
Relating to that, it's interesting to see Miura keeping the tradition of centaurs being male gendered (at least all the ones we have seen in this episode). Makes for an interesting counterpart to the, at least so far, all female merrows. It also makes me wonder how (if?) these folk are able to reproduce, or how some of these astral denizens come to be. I hope we can get some more hints about the nature of these beings in the next episode, or if not in future conversations there at Elfhelm.
Another curious folk from this episode to me are the horned and deer-faced folk, they remind me of the image of Cernnunos, thought to be a celtic "horned god", so it strikes close to home to a lot of these folk source inspiration. The antique imagery of this idol is depicted among wolves, deers and other animals too, so it's quite reminiscent.

Still entranced by all the imagery in this episode. What a celebration for this long awaited meeting.