In my world, there are spirits who can "trade" with humans. The trade is done when a spirit swears to gods to be a human's servant for using a specific spell (for example, in case of fireball, the spirit must create the exact same fireball the human demands and send it to the exact destination using its abilities), and in exchange the human accepts to make a specific sacrifice once and for all (for example, this could be "losing the ability to sleep").

Trade isn't done until both of them are fine with the trade.

Spirits can only trade with one person at a time, but they can trade more than once in their lifetime. Until the human dies, they can't trade with anyone else.


  • can't be seen by humans, except in dreams
  • don't have bodies
  • don't need to eat or consume anything
  • are immortal
  • can speak any language, and can enter any dream
  • know only 1 specific spell
  • are a separate race

My question is, why would a spirit trade with a human?

  • 2
    $\begingroup$ I might have added another answer, but you've already accepted one! I think the rule of thumb is: Never accept an answer until 24 hours have passed since you asked your question. Since members of Worldbuilding come from all sorts of time zones, you should give everyone a chance to respond. :) $\endgroup$ Commented Nov 1, 2018 at 3:00
  • $\begingroup$ Is the spirit a Human that died long ago or a separate kind of entity/race? $\endgroup$
    – Magus
    Commented Nov 1, 2018 at 13:32
  • $\begingroup$ A separate race. $\endgroup$ Commented Nov 1, 2018 at 15:47

8 Answers 8


Free Trade is mutually beneficial by definition: each party values what it receives more than what it gives up.

Spirit could get more actual spirit power from what the human gives up, or entertainment, or bragging rights.

Spirits do not consume anything, but they need a source of power. Humans trade gives them that power. Even if they do not need power to survive, it can enable them to do more things, travel further, etc.

Spirits need entertainment b/c their immortal lives leave them bored of most things, but they enjoy observing the randomness of human emotions and their reactions to powers and curses from spirit trade.

Finally, even if humans themselves are not entertaining, there is competition between spirits on who can get a more powerful human to trade with them, or to give up the most. Kinda like fishing by humans, where you mainly brag about size of the fish.

Note that while the trade is "forever", I assume it only lasts until the human dies. Which is a very short period of time for immortal spirits.

Edit: if you say that spirit can only trade once per its own infinite lifetime, then either all spirits have traded already, or none are interested in trading.

  • $\begingroup$ I edited my question. $\endgroup$ Commented Oct 31, 2018 at 19:45
  • $\begingroup$ On the "Entertainment" - perhaps the only way for a Spirit to experience the Material World is through the senses of a Mortal they are "bonded" with? It's essentially tourism/vacation time for them. $\endgroup$ Commented Nov 2, 2018 at 11:01


car collection https://www.independent.co.uk/life-style/motoring/a-look-inside-the-car-collection-of-michael-fux-a7950721.html

Why does this dude have so many cars? He can only drive one at a time. He has them because he can, and he likes them, and they are bragworthy beautiful things, and then when he visits his rich friends he has something to talk about. Maybe he trades cars with them because he likes specific types of cars for his collections.

So too the spirits. They cannot really use the things the humans give them but they collect that kind of stuff. When the spirits get together they pore over their collections, trade, comment, brag and so on.

One other thing a spirit could do is trade something a human gives up with another human. Fireball spirit might find someone who really wanted a sound nights sleep, and exchange for sleeping (which Fireball spirit has in its collection) will give up the ability to whistle through her nose. Fireball spirit is a whistling aficionado and so makes the swap and improves its collection of various whistling powers.

  • 1
    $\begingroup$ @Sensei. trade is a contract with a human. Shouldn't spirit be released from that contract once the human dies? That's how it works with contracts between humans ... $\endgroup$
    – Bald Bear
    Commented Oct 31, 2018 at 19:15
  • $\begingroup$ @Sensei - one and done? That fireball spirit is tied to that one human waiting for the chance to make its fireball spell? It seems like one fireball spirit could have a lot of human customers. What is the chance they all want fireballs at once? A person probably goes days at a time with no call to make a fireball. . $\endgroup$
    – Willk
    Commented Oct 31, 2018 at 19:23
  • $\begingroup$ @BaldBear makes sense, edited the question. $\endgroup$ Commented Oct 31, 2018 at 19:32
  • $\begingroup$ @Willk trading is a divine action, and gods may not accept his swear if the spirit is already a servant for another human. $\endgroup$ Commented Oct 31, 2018 at 19:36

The sacrifice actually carves off a portion of the person't soul or animating spirit. The spirit either consumes these pieces to sustain or enrich itself or it trades them to something that does use them.

Maybe some high level being is creating an art installation: The concept of taste. It wants the ability to taste different things from several different beings (and the same thing since different people may taste salt differently) so it can perfect it's masterpiece.

There could be a demon who hates humanity and is willing to pay for anything that diminishes humanity.

The main thing is that the spirit itself may or may not be able to use those sacrifices but if the portion of the person the sacrifice represents can be traded, it doesn't matter.

Also, if the other being are so different that they can't interact with the story universe, the spirits are going to be the only contact that the people have. Therefore the people will only know what the spirits tell them or what they can speculate (if the spirits don't talk about it).

EDIT: [addition]

If the spirit can truly only trade once (instead of once for each spell), maybe it is the trade that lets it evolve into the next higher form of spirit. Maybe the spirits are the grubs of the spirit world.

  • $\begingroup$ Nice answer. For the speculation part - there are legends and stories about people trading with spirits, so people already know about the spirits. $\endgroup$ Commented Oct 31, 2018 at 19:40

They might take whatever the human gives up and use it to elevate themselves above a spirit

  • $\begingroup$ Why would the human give something so big that it elevates the spirit? The human doesn't have to trade with the spirit. $\endgroup$ Commented Oct 31, 2018 at 18:45
  • $\begingroup$ @Sensei trade is not a zero-sum game :) $\endgroup$
    – Bald Bear
    Commented Oct 31, 2018 at 19:13

This is a symbiotic or parasitic relationship,

The spirit doesn't really care much what the human sacrifices (although some have preferential tastes) they obtain the energy needed to exist from the act of sacrifice, specifically the feelings of loss created thereby. Humans don't typically have access to this psychic energy anyway so it's possible that both parties can benefit.

Of course it's also possible that a poor deal can be struck causing madness in the human (the stronger the emotions the better for the spirit involved), or a deficit of energy provided if the human doesn't tend to dwell on the sacrifice made. Unfortunately in this case these deals are similar to a geas and can only be escaped by extreme measures and in very rare circumstances.


Your description of spirits made me think of them kind of like "pets". You make a deal/sacrifice and "earn" the loyalty of that spirit for life.

I'm gonna take this statement as the base for my arguments:

Spirits crave for things they can't have - but humans can.


That being said, spirits would try to make deals to fulfill their needs/desires/whims, like a spirit Shark that exchanges being able to sleep for the hability to breathe underwater. For that particular spirit, sleep is an unique delight - 6 to 8 hours where it gets to dream, to free it's mind in the vast and wild realm of infinite possibilities that is the Dream World.

From this point you can get several other sources of pleasure or entertainment, and those could prove to be some very difficult choices.

Would you give up laughter in order to be able to fly, for example?


This option kind of hurts your "one sacrifice, one time, for a power" but it sounded nice to me, so I will give it to you as a bonus.

Just as humans, spirits need nourishment to be able to live indefinitely.

Picture a spirit horse that loves the taste of apples. Since he is a spirit, he can never touch an apple or feel it's taste - or even better, it might be the only thing that it can feed on.

It's only logical that it will try to trade eating apples for the ability to cast fireballs, for example. The caster will never again be able to feel the sweet taste of apples (which now belongs to the spirit) and, in addition to that, he needs to take a bite off an apple before casting his speel - a fruit that now has no taste whatsoever.

You can also play with this. A tastier apple will produce a better fireball than a sour apple. A green apple might have different effects. A rotten apple as well.


It is how a spirit reproduces. If you have traded with a spirit when you die you become a spirit yourself.


Spirits may see some bigger picture gain of the exchange with specific humans and aim for some long term agenda?

Spirits may find themselves to be connected with humans, hence chose to trade with them as to aid a loved one?

To gain information in the form of Experience?

Just some ideas,



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