I don't think the Calasperan background has been posted yet, so I guess I'll break tradition and do it. ZeaLitY, Aitrus and I hammered this out from several separate concepts a few hours ago.
According to what I've got written down, it takes place right after the Glenn scenario, in which the Vanguard is introduced, along with Serran and the Vanguard's Three Stooges, Renault, Roget, and Luther. The party spotted Sorin there, and after seeing him in multiple times think he's connected to whatever's happening to the various time periods. Belthasar figured out how to use the Dragon Tooth to track all occurrences of any particular life force after 65MBC. They spot Sorin in 11998 B.C. and head there to confront him. Magus and Schala request to be taken along for this, so they head off. When they get out of the time portal, though, they find themselves in the middle of a city under the waves, a few hundred kilometers north of where Zeal used to float. This is that mini-Coruscant city I mentioned earlier, except that the architecture is distinctly Zealian. Belthasar can't even believe this place still exists. He tells them about the Zealian Schism; basically, the Zeal you see in the original CT wasn't the original Zeal, but rather a secessionist nation. The city they're in right now is Calasperan, the capital of ancient Zeal. According to Belthasar's story, it was overtaken by a flood shortly after the skyborne version of Zeal became operational and presumed lost. At this point, Melchior comes on the comlink and says that at one point, ancient Zeal faced an energy crisis. The King advocated the use of elemental magic and conventional technological advance to overcome the problem, while the Queen decided that the newly discovered form of magic, codenamed Lavos energy, was the best way to fix it. This dispute ended up not only splitting them apart, but their kingdom as well. The Queen went up into the sky nation, taking with her a very young Schala; at this point she was pregnant with Janus. This is all news to him, since Schala wasn't old enough to remember much of anything.
Belthasar instructs the party to talk to whoever's in charge there about getting some extra gear; not one but two members of the Zealian royal family are present. They immediately march to the palace and demand to be let through. When they reach the throne room, they're greeted by none other than King Zeal, who is positively overjoyed to see his progeny and offers Crono free room and board and a special card that gives him a discount on every good and service in the city, meaning you can buy some higher-end gear for your party members. For a while, Crono is split from the Zeal siblings to explore the city and gain insights as to its nature. Magus and Schala, however, are spending time with their father. As Crono accomplishes various quest-related tasks around the city, cutscenes occur of the siblings talking with their dad. Janus is a major focus here; a true family and security is all he has ever wanted because he never had it. He worked his arse off both to defeat Lavos and to retrieve Schala, and now that he has his father back it seems like he doesn't have to fight anymore. He and his sister could live out the entire rest of their lives in Calasperan, unmolested by history or by conquering warlords; hence, the sequences with the Zeal family here are something akin to Darth Vader or the Emperor trying to tempt Luke to the dark side. And as in that case, the temptations turn out to be founded on bullshit. At the end of this whole sequence, something undetermined relating to a revitalized Queen Zeal, Crono's confrontation with Sorin, and every relevant thing that happens in ZeaLitY's above post occurs.
The mystery of Calasperan: Calasperan is a condensed form of Cala Ataperistan, the Castle of Fire. It's a stronghold referenced in the travels of Marco Polo as being the home of the Magi who came and worshipped Christ; obviously they are relevant here in the form of the Gurus.
Calasperan appears to be the true approximation of a Zealian paradise, save for one thing; it's yet another twisted occurrence dreamed up by the Frozen Flame, and perhaps the grandest in magnitude save the ridiculously mind-blowing shit that I haven't told anyone except ZeaLitY, mainly because it isn't revealed until almost the end of the game. The original Calasperan was destroyed in the wave of natural disasters sparked by Lavos' 12KBC awakening. Only King Zeal survived; once he found the Frozen Flame, he thought it would be nice to resurrect his old home as an illusion of sorts. King Zeal is a deluded man who has been possessed and twisted by the power of Lavos. Calasperan is now effectively a "dream city" that will perish along with all of its people if King Zeal is killed, because the Frozen Flame will then have no Arbiter to sustain the illusion. This lends a moral aspect to this quest as well. This refers back to CC's quote about being able to simulate the soul, and also to a theory several Compendium members, including GrayLensman, Aitrus, and I formulated about the nature of souls in Chrono Trigger and how they're apparently able to defy the laws of special relativity, which dictate that they shouldn't be able to interact with mortals; souls are not pure energy but rather a sort of reaction between the physical universe and its metaphysical fabric, which comprises time and the will of the universe. Basically, the Frozen Flame has recalled Calasperan from an alternate timeline in the Tesseract, much as the planet does for Terra Tower in Cross.
Thoughts?