anything is sufficient, really, haha! though, a link to a picture in my gallery or a sentence telling people what kinds/genres of stuff i generally create would be cool, too, if you'd like. that's awesome, thank you so much!

Those are very good questions on which subjects I must learn more in order to answer fully. US copyright law defines a creative work as any recording of that work, and does not extend protection to ideas or concepts, as specified in Title 17, Chapter 1. Specifically, the quote is:

§ 102 . Subject matter of copyright: In general28

(a) Copyright protection subsists, in accordance with this title, in original works of authorship fixed in any tangible medium of expression, now known or later developed, from which they can be perceived, reproduced, or otherwise communicated, either directly or with the aid of a machine or device. Works of authorship include the following categories:

(1) literary works;
(2) musical works, including any accompanying words;
(3) dramatic works, including any accompanying music;
(4) pantomimes and choreographic works;
(5) pictorial, graphic, and sculptural works;
(6) motion pictures and other audiovisual works;
(7) sound recordings; and
(8) architectural works.

(b) In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work.

There are two ways that the negotiation of creative and profit rights between the commissioner and myself could work that I know of, under US copyright. For one, the commissioner and I may enter a written, commission agreement: no recording is necessary, and rights over the work I create will be granted to them automatically. The other way requires the commissioner to create a recorded account of their world in order for them to legally have rights over whether or not I am allowed to profit from my work.

In the first way, the work I create for their setting will be considered work for hire, under Title 17 Chapter 1, as part of a collaborative work, and the commissioner will own the copyright to all creative works that I have signed over, unless we both explicitly agree otherwise in the written document.

Specifically, the Title 17 Chapter 1 document defines a work made for hire in the following text:

A “work made for hire” is—

(1) a work prepared by an employee within the scope of his or her employment; or

(2) a work specially ordered or commissioned for use as a contribution to a collective work, as a part of a motion picture or other audiovisual work, as a translation, as a supplementary work, as a compilation, as an instructional text, as a test, as answer material for a test, or as an atlas, if the parties expressly agree in a written instrument signed by them that the work shall be considered a work made for hire. For the purpose of the foregoing sentence, a “supplementary work” is a work prepared for publication as a secondary adjunct to a work by another author for the purpose of introducing, concluding, illustrating, explaining, revising, commenting upon, or assisting in the use of the other work, such as forewords, afterwords, pictorial illustrations, maps, charts, tables, editorial notes, musical arrangements, answer material for tests, bibliographies, appendixes, and indexes, and an “instructional text” is a literary, pictorial, or graphic work prepared for publication and with the purpose of use in systematic instructional activities.

In the second way, a commissioner could authorize me to create a derivative work based on recording/s of their setting's details that they have already made. Under US copyright law, any creative work is automatically considered copyright to its creator, so if the commissioner were to present me a *written or otherwise recorded account* of what their world is so far, how it works and so on and so forth, they would own the copyright *to that work*, and anything I create based on that work would be considered a derivative work as described in Circular 14 - alternative link to a more detailed webarchived version here - and they would have the right to say whether or not I could profit from this work.

[contd.]