Alright.

Here's me putting my money where my mouth is (over in this thread)

Traveller using Sorcerer

1.  Humanity

Humanity is human decency(tm).  Caring about people in an active sense, like (for example) Doctor Who or Star Trek.  Actively interfering to help people who are suffering or worse off than you.

So, ignoring the guy getting mugged in front of you is a Humanity check.  Ignoring some starving guy is a Humanity check.  Ignoring someone being abused emotionally or physically is a Humanity check.

Killing someone is a humanity check, especially if you don't have to.  Think code of honor/wild west kinds of justice.  See Firefly/Serenity.

Invading someone's privacy (say, with Telepathy), also counts.

Psionic powers will also interfere with this because, for example, when you can read minds and feel emotions, you become far more aware of your fellow sophont's plight.  You become far more aware of abuse, wrongdoing, and pain.

Furthermore, if you reveal your psionic status in some way, you can expect abuse and pain to come your way.  Do you dare defend yourself, risking your own Humanity to defend yourself?

At zero humanity, you are a soulless monster, willing to do anything to keep your ship running, to keep your own hide free and safe, and every other man, woman, child, and alien is out for only themselves.  Congratulations, you're a psychopath.  Losing humanity is all about trade-offs.  Making choices that compromise other people's life, liberty, happiness, and security for your own.

2.  Descriptors

2a.  Stamina
     o Hi-g Homeworld                                     
     o Military Regimen
     o Zero-g Experience
     o Barbarian
     o Wiry

2b.  Will
     o Driven
     o Gift of Gab
     o Sneaky
     o Brainiac
     o Well Travelled

2c.  Lore
     o Psionics-related
         o Latent
         o Zhodani-trained
         o Psionics Institute Alumni
         o Naturally Gifted
         o Psi-Drug Addict
      o Technology-related
         o Ship Captain
         o Engineer
         o Tinkerer
         o Traveller
         o Crew

2d.  Cover/Career
     o Scout
     o Merchant
     o Noble
     o Navy
     o Ex-Grunt
     o Scientist
     o etc.

3.  Demons

Two independent kinds of Demon.  If your Lore is high enough to have multiple descriptors, you can pick one from each type, and your lore applies to both.  Otherwise, you are restricted to the kind of demon your lore descriptor applies to.

3a.  Technology

Technology in Traveller is largely recognizable to most modern folks, but at the same time, contains a liberal dash of outright weirdness, like Jump Drive or the like.

For a bit of technology to be considered a Demon, it needs to be a piece of high tech.  It can be a handheld computer, it can be a whole starship, it can be a smaller thing like a grav-vehicle, or even a particular gun or Vacc Suit.  It might be a robot.

For a large play group, it might even be a Starship subsystem.  For example, the "Flight" movement ability might be attached to the "avionics demon" that the Pilot has bound.  The "FTL Jump" movement ability might be connected to the "jump drive demon" that the ship's Engineer has bound.  And so forth.  In this way, a Starship as a whole might be made up of smaller individual demons which are bound to various different sorcerers, allowing a "single" demon -- the ship -- to be bound to multiple players, after a fashion.

The key here is that this bit of tech has to have a kind of personality.  It needs to be a bit prone to breakdowns or quirky
behavior.  Think The Millenium Falcon or the Batmobile or Boba Fett's Mandalorian Armor.

Cybernetics can be in play, so a limb replacement could be a Demon, in this context.


Demon Technology 'Need':

The needs of technological devices will vary, but only within a certain fairly well defined range.  They will cost money for upkeep, and maintenance (ie, Lore rolls).  If you can't do the maintenance yourself, you will have to pay someone else.  The device will also require a power source -- fuel or batteries or something.  Again, this will require money.
                             
Starships need not just regular maintenance, but annual maintenance, as well as costs such as life support, maintenance, repair, fuel, and berthing costs.

Note that what we're talking about here isn't that they Need Money. What they Need is the power source and the fixing up.  The raw materials, food, and oxygen for the life support system, and a berth to be parked in.  There are ways of getting these things that don't involve paying for them.  If you have (or can get) such an arrangement, good for you.
                             
Money seems like a small thing.  But when you don't have it, and your Technology/Demon starts to become rebellious/obstreperous/malfunction-prone, well, you might be willing to do things you don't like to think about to keep yourself in
operating funds...

Just like in real life.


Demon Technology 'Desire':
                             
Technology desires to undertake it's function.  Starships want to fly between the stars.  Laser swords want to slice through things.  Guns want to shoot.  Computers want to think.  Robots want... to robot (or undertake whatever other function they've been made for).
                                 

3b.  Psionics
                             
Psionic powers are feared and reviled within the 3rd Imperium.  In fact, they're outright illegal in many places.  Certainly open displays of Psionic ability run the risk of open discrimination, if not outright lynch mobs.

Psionics demons are always parasite demons.

         
Psionic Demon 'Need'

Their Need is rest, meditation, and solitude.  These can be hard to come by on a crowded starship with a busy schedule.  These requirements will vary, but will be in addition to a regular nights sleep.  Perhaps one hour per Power use?  I dunno.  Probably need a firmer rule of thumb here.
                             
If you are Psi-Drug addicted, they will also require regular supplies of these (illegal) medications.
                                                           

Psionic Demon 'Desire'       

Like pieces of technology, Psionic abilities want to be used.  You will be pushed to teleport, to read people's minds, to grab things with your telekinesis.

This risks 'outing' you, which will draw violence and persecution to you.

What I wonder is what about all the other millions of jump ships out there? Are they all demons too? Is every captain a sorcerer? That's a lot of sorcerers for a game that relies for part of its impact on sorcerers being rare.

If not, what does my demon ship do that their ordinary one can't? Why should I put up with Need and Desire, if I could just buy the equivalent in technology without that?

I say they're all sorcerers.

Why should they have to be rare?

Sorcerer is a package -- part of that package is making each player character one of a handful of unique individuals who can command things that violate reality. If you take away the uniqueness, you've moved out of the thematic game package that is Sorcerer. You're using the mechanics for something else.

I'm not saying you can't play Traveller with Sorcerer mechanics. My questions is why do it when you cut out the heart of Sorcerer to do it?

Sure, I see what you're saying.

I guess I just don't see the uniqueness as being as integral to the heart of the game as I do the Humanity and Sorcerer/Demon relationship mechanics.

Shrug.

Assuming you're playing in the Third Imperium, the setting is pretty large.  What makes the players special is that they are the players.  Not that they are the only people who have demons.

In Traveller in general, the player characters belong to an elite in the Imperium -- that of the starfaring class.  People not tied strongly to any of the individual worlds they visit, or to those worlds governments, restrictions, or limitations.  Their starships and technology is part of what makes them different from the locals, and so in my head, it made sense to map "Starfaring Traveller" to "Sorcerer".

There are a LOT of different ways to make that mapping, and probably all of them could be good games.

I don't personally see a problem with giving everybody a Demon.  It's not going to be a play style for everybody, but I don't see as how the core Sorcerer meta-setting requires Sorcerer Scarcity.  Perhaps I'm missing something?

Sorcerers being rare is a basic assumption of the default modern setting in the core book. This assumption has no reason to carry over to a more fantastic setting. I see no problem with every starship captain being a sorcerer.

Further, if you walk into a room with a thousand people in it, how many captain a starship?

There might be only half a dozen on any given planet at any given time.