[@RoadkilBanana]
Hello there. Thanks for the interest. This bloated vanity project of mine is still trudging along towards a ready state where everything I have will be listed out and updated. For now though, I can point you to the two main posts having to do with fusion. As part of the hard mechanics, check out the [url=https://www.roleplayerguild.com/posts/5484888]last section of the first post under "Fusion Basics"[/url]. It's based off of the fan-game Infinite Fusion, if you ever heard of that one. The section might be due for a little update soon, but generally that's what it'll look like.

And for what initiates fusions in the RP, check out this [url=https://www.roleplayerguild.com/posts/5497141]post having to do with a certain class of special items in the game called Coalescite.[/url] I hope that helped a little. Basically you can either make a fusion who acts just like any other pokémon (and stays like that permanently), or your pokémon can become part of a fusion later that's literally a two in one (with the help of said special items). I like to think that presents a good deal of freedom for what kind of character you might want to make. Let me know if you have any other questions.

(P.S. - Items like those crystals have additional descriptive text to each of them once you move your mouse cursor over them. Sorry if you already knew that. Just wanted to be sure.)