I got a wag that the red court placed their repository in New Mexico at such a dragon hoard location and consequently paid for it.

iirc only Harry, Martin, and Susan knew the location of that Red Court vault. Is it standing abandoned in the desert, just waiting for Harry to remember and use it as his personal arcane walmart?

If so, is it a coincidence that Harry's first sexual/romantic relationship was with his 'sister' (in legal semi-technicality, anyway), who happens to be named Elaine?

Elaine Mallory, no less. If that's not a nudge towards Le Morte d'Arthur then I don't know what is.

I'm leaning towards a reincarnation/echoes of the past explanation myself, but there are so many references back to Arthurian myth that I'm going to be honestly surprised if Harry passes on Amoracchius without pitching a tantrum and stabbing it into a stone first.

I do think that whatever else is going on, the players in the past aren't necessarily repeating in the same roles or following the same paths- hence Morgan Le Fay is Harry's (Merlin's?) mother, and the role of psuedo-incestuous sister is instead played by  the Lady of Shalott (Elaine). For that matter, OG Merlin's father was rumoured to be an incubus- hello, Thomas.

If I recall correctly, in some traditions Arthur was mortally wounded by Mordred but didn't die- he was instead entombed at Avalon to sleep until his messianic return to save the realm in the hour of greatest need. British-seeming stasis-prisoner on DR doesn't seem like such a stretch in that light, but I've got even odds on Good King Johnny Marcone stepping up to the plate. He's already been betrayed by a lover, but instead of sleeping around 'Guinevere' sold him out to the Denarians.

It's a pretty loose theory and I'm not familiar enough with Arthurian myth to carry it any further, except that having a prominent antagonist-slash-ally named Morgan probably isn't a coincidence either.