I've been saying this in-game to my friends for over a week now-- my instincts keep looking toward a scythe wielding VOID MAGE as a possibility.
See that ship headed to the moon in the Endwalker's logo? Why the bloody heck did it suddenly remind me of the Tales of Mhachi 24-man raids from Heavensward? Perhaps it is because the interior architecture of that tower in the trailer (with Fandaniel and Zenos) which looked expressively very similar to the ones within the Void Ark raids. Then of course, there were the official new concept images of Endwalker which were tweeted online and then my blood got racing.
Then I really want digging-- re-watching lore related cut-scenes, replaying the Void Ark raids for my relic runs and then researching my FFXIV books-- then I remembered. According to the wonderful pages of my Eorzean Encylopaedia (pages 30 to 35) the lore explains that the Mhachi civilization evolved within the Yafaem Saltmoor which is just northwest of the Mor Dhona area-- and they were the originators of the voidmage job-class.
Also has me seriously wondering if some Mhachi survivors have been hiding on the moon this whole time... it will be really interesting to find out if High Void Mage Cessair (Cait Sith's master) has been alive all this time-- very interesting indeed because this tale has been one that has intrigued me immensely since Heavenward's release in 2015. Think about it-- we got in-depth clarifications into the Syrus Tower tale in Shadowbringers and the Ivalice tales are being tied to Gabranth and the Save The Queen arc-- but what about the Tales of Mhachi tale with their Void mages? Yoshi and the Devs may not like tying in new jobs to story progression but there are locales within the game that can support the commencement of the void mage job-- Gelmorra, Tam-Tara and Toto-Rak are a few that come to mind.
*(Gives a silly smirk)*... a scythe-welding Void Mage as a possibility. Could be a silly thought, but weirder things have happened.