Due to me having finished reading Fukayami no Celephais (joke work, later canonized, which takes place in an alternate universe in which Tesla died), I'm going to paste relevant info here:
-Since the WIC managed to finally kill Tesla (Neon's also dead), Golden King "saw the light" and became the leader of "Hope's Fortress", resistance organization against the Society, and the world's greatest hero.
-Rosenkreuz is the headmaster of Marseille Offshore Academia, now repurposed as his resistance organization's HQ. All students in the school are under his protection. He takes the form of a scientist, with a golden mask.
-Mary Clarissa Christie is an student in the Academia who ends up joining the group. Though at first she's only worth for planning, she later receives a power capable of interfering with fate, courtesy of Rosenkreuz.
-Kerkan is a mercenary with the power to manipulate ice. He joins the group while caring nothing for preventing the destruction of the world. He just wants to kill the demon men of the WIC who murdered his little sister (implied to still be Kia in this universe). Grows fond of Mary cause she resembles Kia.
-Ana, an Adept from Valusia, is also a member of the group. She's left in the care of Golden King by her parents, who are later murdered by the WIC. Seemingly lacking the Old One blessing that granted her Adept powers in Valusia, her body is strengthned with Inganock Technology (Crack Engines). Furthermore, Rosenkreuz grants her "Accelerate" (Walther's Art. Given it gets the same description Mary's "fate intervention" power does, it's possible that's also an Art).
-Hilde, originally Steel Princess from the WIC, now goes by her original name of Jeanne. She defected the WIC alongside Rosenkreuz and serves as her right hand woman, and as vice-director of the Academia.
-Athl, protagonist of Valusia, is the group's mechanic. He's in charge of the airship. He falls in love with Xerxes here too.
-Teacher Iru from Inganock is also a member of Golden King's resistance.
-Leonardo Da Vinci has gone to the side of evil, being now Golden King's replacement as Acting Leader of the WIC. He goes by the name of Magi, now. His plan is to activate the Mega Engine Hubris that lies at the end of Kadath, so he can activate the Great Equation to destroy both Earth and Kadath.
-Xerxes is Magi's adoptive daughter. Her Golden Eyes are the key to Mega Engine Hubris' activation. She's kidnapped by Magi.
-Zarathustra continues on the WIC side. He's one of Leo's demon men, and possesses incredible Mesmerism powers, capable of making his enemies to turn into one another.
-Georgious is one of Magi's demon men. He has insane intellect and a mutated brain, which allows him to use Cracking. He's the most powerful Cracking user the WIC has, and also the second most powerful member overall, being capable of rivaling Magi's might. He's always accompanied by a cat type Shadow Man he calls "Ati". All of this implies he's Gii, Inganock's protagonist.
-Astaire (character from Celenaria, coming from the Astaire clan. Do not confuse with Inganock's Archduke) is also one of the demon men. He's the WIC's strongest swordsman, on top of being an accomplished aircraft pilot. With only one jet he annihilated the USA's entire army, on his lonesome. He possesses Golden Eyes, and the Mask of White Death.
-Cornelia's another demon man (woman). Pilot of a Great Scholar Equation Extermination airship, implied to be the Ulamensh (the airship of Celenaria's protagonists). This ship has obliterated many cities already. She's Astaire's lover and fiancée, who calls her Connie (confirming this is Connie from Celenaria) affectively.
-Kashim, Ana's brother from Valusia, is the last of the demon men. He's a powerful, three armed swordsman, who's lost most of his emotions due to having fought in the labyrinth (from Valusia) for so much time.
-Lily (from Sona Nyl) briefly appears in her flying train to tell something to Golden King.
-In the story's ending, Magi manages his goal and activates the Great Equation, beginning the countdown for the destruction of both Earth and Kadath. The ending takes place in Rome, at the top of its Mega Engine Tower.
-Most of the guys from Hope's Fortress are dead, and only the elite remains. Astaire and Connie have fallen, from the WIC's group.
-The WIC has many Engine Weapons at its disposal, including squads of Chrome Bodies.
-Georgious can use his Cracking to perform a "space fixation" power and, with the help of a Scholar Machine which amplifies the power of the Cracking Effect, can turn all of Hope's Fortress' elite into cinders. Kerkan's ice power was able to stop his attack, which would have annihilated them all.
-Magi decomposes his attacking enemies into basic components with a simple wave of his hand.
-Golden King shoots Magi with a beam of light from his golden gauntlet, while Machina (Celephais' protagonist and PoV. He's a synthetic human created by the WIC as the successor to Type Moran in the main universe, with Machine Belt technology, the same one Tesla uses. In this universe, he was created by Adam Weishaupt using Tesla's data as a basis) releases all the lightning accumulated in his body, creating steam with the capability to "rewrite the world".
-Magi tanks this completely unscathed.
-Georgious uses his Cracking to destroy space, managing to destroy half of Golden King's body.
-In a desperate effort, Rosenkreuz takes Magi to the grave with him.
-Georgious, who is shown to have glowing eyes (sekime), approaches in order to kill Machina with his "left hand". Georgious one shots Zarathustra with this ability, and kills Lisa Force, who sacrifices herself so Machina can live. The WIC's plan is still proceeding.
-Athl arrives in scene. Before Georgious can actually gank them, and both planets are destroyed, Athl uses a Scholar Machine to transport Machina to another universe. The main Steampunk universe.
-There, Machina finds another like him (a Machina at the service of the WIC in the main universe), who's on the floor, on the verge of death. It soon dies, and Machina takes its Machine Belt, becoming a pain in the WIC's ass in the main universe.
-Celephais' universe's Earth and Kadath were probably destroyed, as Sakurai said Celephais was quite a literal "apocalypse scenario". It seems Edison's Mega Engine Clock may have been involved in Celephais, since Machina notes it isn't piercing the ground in this universe.
So that's all I remember.