Anemoi

Here. A jamjar game where, upon their arrival, characters lose their memories. Newcomers are brought to the laboratory in the center of the city of Sirocco, where they are employed by the government and told that the way to get memories back is to find anemoi, either out in the wilderness or through taking jobs in the city, and bring them back to the lab for processing.

And once you get more than a few miles out from city limits, the wilderness can be pretty damn wild. There are all sorts of creatures out there, including creatures from the characters' own worlds. Sirocco is the only known bastion of civilization, and its numbers are dwindling -- hence the influx of newcomers. Characters don't know how or why things got to be this way, but perhaps they'll find out sooner or later...

Tropes used in Anemoi include:

Back from the Dead: Characters who are killed discover themselves on a train headed to the afterlife. Should they choose to get off at the Sirocco stop, they'll return back to life.
Butt Monkey: There's quite a few already, but Axel dwarfed the rest by an order of magnitude when he was around.
- Kotetsu comes close, especially in the adventure logs.
Coincidence Magnet: Not any particular character, but rather the Ermis Suites themselves. The RNG has come up with some incredible rooming assignments. Archer and Shirou, Prussia and America, and Jaime and Booster all ended up as roommates. The Random Number God certainly has a sense of humor for this game.
Dead to Begin With: Danny is half-ghost, so he only half counts -- but he showed up in ghost mode, and doesn't remember that he's still alive.
Eldritch Location: Some of the areas within the wilderness can be these.
Everyone Can See It: Shirou and Rin. However, Vriska seems to think they're waxing black for each other.
Expy: These sometimes appear in anemoi-gathering expeditions. For example, Shirou, Rin, Dave, and Vriska went on a hunt and found themselves fighting walking mushrooms, flying turtles, and a giant, fire-breathing turtle in a lava-filled castle.
- There was also a three-day event that consisted of the moon plummeting toward Sirocco. Sounds familiar, right?
Fantasy Kitchen Sink
Game Master: The moderators, of course, but the game allows players to run their own anemoi-gathering expeditions if they so choose.
Jerkass Gods: The "gods" (for lack of a better term) in this setting, including Kyogre and Shiva, are responsible for the amnesia in the setting. Doomtrain may be the exception -- no one can remember it causing their amnesia.
Killed Off for Real: In contrast to Back from the Dead above, characters who choose to stay on the train are permanently dead and can never be apped back into the game again.
Laser-Guided Amnesia: Part of the premise.
Mega Crossover: Not just the characters -- the indigenous life and even mechanics of other worlds can be introduced into the game, like the magic from Elibe or the Guilty Gear world or the Bands function from Final Fantasy IV: The After Years.
Mineral MacGuffin: The anemoi.
Non-Player Character: The "gods," including Doomtrain, Kyogre, and Shiva.
Noodle Incident: Isshin, Joachim, Yuri, Ky, and Lyon went on an anemoi hunt...and had a miserable time of it. None of them will ever talk about it.
Official Couple: Shirou and Rin.
One Steve Limit: Averted with Rin Tezuka and Rin Tohsaka.
Ontological Mystery
Shipper on Deck: Joachim and Ran ship Ky/Kaguya.
"Shut Up" Kiss: Shirou gave one to Rin.
Suck E. Cheese's: Sirocco has one! Kaguya tried to take Ky there. For Valentine's Day.
Summon Everyman Hero: Characters range from the superheroes of Tiger and Bunny and The DCU to normal humans like Tsuruya.
Super Team: A bona fide Justice League, or at least as bona fide as one can get with Booster Gold as its manager and only member actually from The DCU.
Theme Music Power-Up: Occurs frequently in anemoi-gathering logs. May overlap with Awesome Music.
Time Travel: Often casually utilized by Dave Strider, but special mention goes to the Ao Oni plot, in which Dave and Supernova came back to the present of the RP from a Bad Future in order to Set Right What Once Went Wrong.
Trapped in Another World
Wide Open Sandbox: Word of God says that, while there will be self-contained, mod-run plots, the game does not have an overarching plot. This leaves characters and players to do much of what they please. Characters can get jobs in the city, go on trips into the wilderness to explore and collect anemoi, or anything else one can do in a city of Sirocco's size.
Write What You Know: Sirocco's layout is based on the city of Halifax, Nova Scotia -- which is where the founding mod is originally from.