The 'Rules' on elemental magic (I assume you're talking about this article) are more guidelines than actual rules, magic is something that can't really be defined by rules as each person's view of it is generally unique. If you're joining an already existing RP with magic involved, try and follow the way that the author has used magic, and try not to introduce anything that would contradict what's already been done, unless it's a free-for-all type of thing where you can pretty much use whatever you want.

As for joining RPs, just check out their corresponding OOC thread and post an application (or whatever's required to join), either that or PM the thread creator. Just make sure to check first if the thread is still alive and always be sure to either read everything posted beforehand or ask for a summary to get a gist of the plot.

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