something interferes with Harry’s winter mantle. We saw in previous books that there are connections between the Greek myths and the fae (Hades having statues of the queens, Harry calling the crone Hecate to summon her) so I suspect Harry’s visitor is from that pantheon. Coupled with the appearance of the pot, I think the visitor is
https://www.theoi.com/Titan/TitanisMnemosyne.htmlUnlike her brother Titans, the female ones were never cast into Tartarus by Zeus. So she’s around. Also as the Titan of memory maybe mere thoughts can bring things into existence around her.
Edit: and don’t forget the huge footprints from chapter 1