The dragon thing that causes the trainwreck was instructed to save Joey and kill Xefros so that Fiamet can have a weird alien all to herself. Why else would the Deercat be presant but not Xefros? Why would it choose to save a random alien over it's son's boyfriend? After that dragon incinerated Xefros's head off or something it probably thought "Well, my son's boyfriend is dead, might as well follow that weird looking chick he made friends with.". The island that is shown in the concept art from Sahcon '23 is where Fiamet lives, the dragon also incinerated the contents of Joey's inventory so that she would be more dependent on Fiamet.
Joey and the Deercat arrive at the gates of a long abandoned temple dedicated to a religon that is widely believed to have no living members. As they enter, they discover that Fiamet has converted the lobby, for lack of a better word, of the temple into a hive for herself. Joey and Fiamet chat a bit. There is a scene where Joey brings up Xefros's death and Fiamet is like "Lol, whatever, have you heard about the newest yaoi?" and Joey loses her cool and calls her a selfcentered little bitch and goes on a rant about how she hates this goddamn planet and that it would be better for her to have been eaten by the monsters back in Act 1. In an attempt to cheer her up, Fiamet says that Cridea is a close friend of her's and that she'll ask her to give Joey VIP status at Jeevik Week. This backfires and only makes Joey even more angry. At this point, Fiamet gives up and decides to just kill Joey. The Deercat defends Joey, and while Fiamet is trying to stop it from killing her, Joey flees. Joey dashes through Fiamet's massive hive and is able to enter an area that was closed off eirlier. If you explore this area, Joey will find a hatch that leads into the actual temple. There is a game over screen where if you do not find the hatch quick enough, Fiamet will catch up to Joey and kill her.
Joey climbs through the hatch and discovers that most of the temple is under the seafloor. Not like under the Marina Trench, under the floor of the island (Joey can't handle such extreme pressure anyways). She then explores the various rooms of the temple. She spends this segment exploring, marveling at the designs of the rooms, and refilling her inventory. As she explores, she deducts that the religon that built this temple revolves around a prophecy that an alien will arrive to Alternia and vastly improve the troll race, and that it is their responsibility to build a portal that will bring them over and was lead by the weird deranged looking troll revealed in Sahcon '22. The further into the temple she goes, the less organic and more modren the inteior design gets. She comes to the final rooms of the temple, the weird bathroom looking thing with several cauldrons of a weird slimey substance, and the hallway looking thing. She discovers several failed attempts at creating portals in the first room, as well as the mummified corpse of the leader of the religon. She goes into the next room, which is filled with portals that lead to various places on Alternia she decides to try her luck with one of the portals, what else is she gonna do, just sit around and wait to strave to death? The portal lands her in a spare room in Cridea's hive.
Cridea discovers Joey and is estatic. She is a part of the religon, and never thought she would live to see the prophecy come true! After they get to know each other, Cridea figures out that Joey's character is far from what the prophecy foretold, but still has hope in her. Joey summerises her entire adventure from raking leaves in her yard to teleporting to Cridea's closet, and Cridea reveals her connections to Dammek. She and Dammek are both members of the religon, Dammek is more focused on the revolution aspect of the prophecy, and Cridea is more focused on the alien themself. She reveals that Xefros and Fiamet, although Dammek called them "tetraches", don't know about the religon, only the vague ideas of revolution and finding the alien, respectively. Joey wonders if the "...weird rituals that me" that Xefros mentioned in Act 2 were part of the religon.
Cridea gives Joey VIP status at Jeevik Week, and Joey goes around the island, taking in the attractions and chatting with the new trolls revealed during Sahcon '22. The game ends with a message saying that Joey's adventure will continue in Act 4.
But thats just my personal theory
I might think about this a bit more and change this a few days later.