A Lovecraft envelope, postmark 9th June 1934, with a note to Clark Ashton Smith on the back…

Ar-Ech-Bei [Barlow] wishes you would fcall [phone? call / tell?] him as much as possible about H2UICQU01QMN2HAH [Hziulquoigmnzhah], the paternal uncle of Tsathoggua – cf. “Door to Saturn”.

My guess would be that this might relate to tweaking Smith’s “Door to Saturn” (pub. Jan 1932) before a reprint, so as to align it with the emerging Tsathoggua aspect of the mythos…

I have done what I could toward elucidating the genealogy of Tsathoggua, and am sending Ar-Ech-Bei [Barlow] the result of my delvings into the Parchments of Pnom, the chief Hyperborean authority on such matters. Pnom [R.E. Howard?] has much more to say about Tsathoggua than about Cthulhu, Yog-Sothoth and Azathoth; but no doubt you have access to other records, mainly concerning these entities; and I’d be glad of more specific information about them. As I am pointing out to Ar-Ech-Bei, Pnom’s account of Ts. can be reconciled with the legendry told to Zamarcona in ‘The Mound.’ The myth, through aeons, was varied in the usual mythopoeic fashion by the cavern-dwellers, who came at last to believe that merely the images of Tsathoggua, and not the god himself, had emerged in former cycles from the inner gulf. Ts., travelling fourth-dimensionally from Saturn, first entered the Earth through the lightless abyss of N’kai; and, not unnaturally, the Yothians regarded N’kai as his place of origin. Undoubtedly the god now resides in N’kai, to which he returned when the ice overwhelmed Hyperborea.” (thanks to Will Murray for the 1934 Lovecraft to Smith letter extract)

An interesting insight into the care Lovecraft took, in co-ordinating the merging of the emerging mythos.