For those of you without the Sundered Eagle, the island of Delos is a floating island in the Tribunal of Thebes that serves as the tribunal site, where magi dump vis into a lake as a means to feed the sponsor spirits of their respective covenants. Zeus has forbidden births and deaths there and everything suffers from feelings of restlessness, so nobody stays for long. It has a mostly Magical Aura throughout and houses the tribunal's treasury and is guarded by Magical Nymphs.
Mythologically, the island is actually the transformed state of the titaness Asteria. She was fleeing Olympus from Zeus (she sided with the gods during the Titanomachia), flying down in the shape of a quail, tried to hide in the Aegean sea, got chased by Poseidon, and then turned herself into an island to escape him. Later her sister Leto, who was less successful in escaping Zeus, was being hounded by Hera, who forbade anyone from sheltering her, but Asteria ignored Hera and Leto gave birth to Artemis, then Apollo, on Delos. As a result of the twin's births some pillars grew to anchor the island (in The Shattered Eagle, these pillars have crumbled and Delos is free to roam again). Delos was then an important center of the worship of all 4 gods.
Note that Hera basically forgave Asteria for doing this on account of the fact that she refused Zeus's advances in the past, proving that Hera was willing to let some things slide if you didn't sleep with her husband when you got the chance.
Okay, so on to the mechanics. What is Delos? I can see several options:
1.) Straight up Aspect of the Titaness Asteria. Which would mean the island has Might and powers. But the tribunal has been using the island for centuries and you think they would have noticed that. Delos was a barren floating island for some time, however, so maybe the soil that's built up isn't part of the island's Might and thus magi would be less likely to notice (i.e. it's just the underlying rock that's the Aspect).
2.) Island created by Asteria to hide from Poseidon. Pretty straightforward, but seemingly outside her purview - but then turning into an island also seems to be outside her purview, so either way makes equal sense.
3.) Star pulled from the heavens for Asteria to hide on. This would be more in keeping with her powers, as she's the Titaness of Shooting Stars. It might also explain why it floats, being a rather unearthly chunk of rock and why it's got a big honking Magical Aura that causes restlessness.
The reason I'm asking is I'm noodling with the idea of a Mystery cult descended from the Delian priesthoods (probably Leto and Asteria based, given how Artemis and Apollo's priests probably fled to Hyperborea) and what Delos actually is sort of relevant to any cult centered around the island. So opinions and ideas are welcome!