A little of all of the above.
Here's my old transcription; between the two of us I'm sure an accurate reading can be gleaned.
Pentetolothys
Athealogicad
Ylk'eorz
Tetheth Ctulaniacl
Mesca molla nith kol atha
afah on mantha qulta oka
millh azan thal azan ul.
Gelli deuz tort'il am all'i
veuol gthal nk'denil ma
thaeothelphae guil ac'til.
Nevth'ent noctemas tel
paeth byl xun tao zin djai
akh mael thisthe qarnic.
Mor ann mor silvae mor.
Morn ynn morn silvae morn.
Tu'l qui jae tzun tao
ghollill demen atymos al
ill fhwil athac feryne.
[1872]
Cillix yn zolol nedzj seF
Tolnysor bevid. MolH
Holnix xanla tildylT
Usen yn vholl thaelA
Li Noctologolae netheG
Hyss diem alul morN
Unna morn tulwal.
Mesca molla atymos kol
mor unna mor gwyr
cthol aen dag il on al
feryne akyn.
Taehlo geomyntoric
M'Lin L'th Qitha
Bellenoctol
Sempyr
Beneth quin jao azathi chail
Atymos'il fhil ambyri ox
Gothin dalam gyllo ud tempa
[1871]
What's in there?
Everything. Some of the words are English-
ish, some of the words are Dravanian-
ish, some of the words have roots in
Tolkein. I think I even see some Chinese and Latin in there. Along with words like
Qarnic, which seem Eorzean-inspired, perhaps.
Can the entire thing be turned into something logical? That I don't know. At the moment, I doubt it; I tried for a while. But maybe!
What other things do we see in there, though? We thought maybe "Ylk'eorz" was the something relating to Eorzeans via "The Ilk of Eorzea", maybe. "Pentetolothis" looked like a mix of Greek and Sindarin that we took to literally mean 58, or by way of five octets, 40. "Atheologicad" we had a lot of ideas for, logic or knowledge pertaining to either aether or the gods, such as "ungodly" knowledge or "unholy" knowledge, maybe. "Atymos" might be Atomos, Sempyr might be related to Semper. "Noct" seems like an obvious root that pops up.
Oh, and if you look at the first and last letter of each line on the player-right page, from top to bottom:
CTHULHU FHTAGN.
With that, I pass the torch to you!