Setting: Institute of Occult Sciences

There's no such thing as a surface. Instead we have the Underground: a world made of negative space, the kind of subterranean locale you're probably familiar with from many prior sources. The Underground borrows heavily from these sources and from other classic science fiction. It has its Morlocks, its ichthyosaurs, its Newts and Lemurians.

It's also undergoing a technological revolution. Clockwork devices proliferate; train tracks connect the known world; natural philosophy has started to bear strange and alarming fruit. All of it is driven by Weird Science, and most of the science is produced by an Institute that is a little anarchist and very mad.

Players are students at the Institute of Occult Sciences, or at least part of its ecosystem.

My plan is really to run this as a set of parallel duet games and furnish everyone with their own personal subplots, but here are some more generic ambitions, if you're into that:
~ Become something more-than-human.
~ Be recognized as a professor.
~ Establish yourself as a regional superpower.
~ Found or revolutionize a Science.

For extra credit: Prevent the world from being destroyed by superintelligent cuttlefish, or whatever else is metastasizing this week.

This setting is built on Laws, when I feel like it.

The Institute

• All the rules are informal. Professorship is a social construct; there are lectures and labs but you enroll in them by showing up.
• More advanced courses may be available only by invitation. They meet at odd times or in odd places.
• Everyone is obsessed with something, and probably eager to talk about it.
• Many people have sinister motives.
• Academic disagreements are serious business.

The Weird Parts

• "Exchange students" have no distinguishing characteristics and can only be seen in your peripheral vision. They make up about half the Institute's population.
• We have invented messenger lizards and pneumatic tubes but not the intercom.
• The library has many sub-levels and is full of strange objects. It tends not to be actively dangerous unless you take risks, disturb something, or break rules.
• Tall buildings are perpetually wreathed in lightning.
• The groundskeepers don't speak and never leave any skin exposed.

Student Life

• Students must find a place to stay and deal with the practicalities of living there.
• Currency exists, but most people trade favors.
• People are always willing to show you around. They might ask for a small favor in return.
• There are lots of extracurricular activities.

The Sciences:

There are five major Sciences. Each is a magic system made up of a bundle of interrelated techniques and setting details. If you've seen GLOG deltas (Inadvisable Decisions is my favorite) or Stolen World lifepaths it's a bit like those. More of a focus on crafting, since that is my group's particular genre of madness.

Corporeal Science: Study of biological materials. Think Victor Frankenstein or the Darwinists from Leviathan.

Galvanic Science: Study of electricity and magnetism. Nikola Tesla in a universe where the death ray actually works.

Motive Science: Study of motion, including perpetual motion. Produces clockworks, automata, terrible engines, etc.

Lucid Science: Study of information. Can facilitate remote viewing, telepathy, and SCP-esque anti/memetics.

Empty Science: Study of the nonexistent and unreal. Deeply esoteric but has practical applications in necromancy, dream-manipulation, and summoning invisible Presences.

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There are also 'secondary' magic systems which are smaller in scope or less recognized by the Institute. If I think of something cool that meshes with the Underground's aesthetics it can probably be thrown in.

d4 lesser Sciences:

1. Verdant science. Creating Audrey II through cross-pollination, speculating wildly about why anything grows underground.
2. Worm language. Communing with chasm-creatures via drumming and exchange of blood.
3. Transmutative arts. Metallurgy and chemical synthesis, extracting useful substances from tidal effluvium.
4. Aberrant cartography. Mapping the Underground, navigating non-euclidean space, dowsing for ores and ichor.

Backgrounds:

Each comes with two ~things, one functional and another that can be either fluff or a plot hook. In the race/class binary they're more race than class, but there should probably be another 1-2 that are additional flavors of human. 

Dodger: Member of an itinerant subculture that travels the underground by stowing away aboard cargo trains.
~ An old wound. If it impairs a limb or vital organ you might have a mechanical prosthetic.
~ A knack for hiding, evading pursuit, knifework, or another practical skill.

Neo-Promethean: A humanlike being assembled from salts and humours by a student of Corporeal Science.
~ A physiological defect which might be an advantage if viewed from the right angle.
~ A creator elsewhere in the Institute, now disinterested or deceased.

Morlock: An offshoot of humanity adapted to existence in lightless chasms.
~ Complicated mouthparts, customarily hidden with a scarf or a half-mask in public.
~ Lean muscle and an excellent sense of smell.

Illuminated: A person with a sliver of something unreal embedded in their mind.
~ Chronic insomnia. When you do sleep you have surreal nightmares.
~ The ability to clearly perceive things which are only half-there.

Guest: A corpse animated by sentient slime mold.
~ Extreme resilience, owing to your unreliance on human organs or metabolic processes.
~ Fragments of your host body's memories, absorbed when you ate its brain.

Cryonaut: Someone from an ancient era, entombed in a cryogenic corpse-city for hundreds or thousands of years.
~ A deep-time artifact. It might be a possession of yours or an oddity from the Necropolis.
~ A rich personal history which is now basically irrelevant.

Foundling: A lost child adopted by Lemurians. Left behind when the colony vanished.
~ Glowing eyes with complex nictitating membranes for modulating color and intensity.
~ Projective telepathy. You can transmit thoughts to anyone who meets your eyes.

Skittering: An intelligent monster that has integrated into society, typically unique.
~ A totally inhuman body-plan, and probably an alien mindset too. You might lack a social instinct or experience odd cravings.
~ An eccentric wardrobe. Clothing is a way to signal personhood and lack of hostility.