Did you see /char/create in fiddler? I've never seen it sent. I just guessed the /create part.
I've tried finding the correct parameters for this url for a long time. The url exists nowhere in the client, it isn't sent by my client at least (when you create a character in game you send the CREATE packet). My assumption at this point is that this url (and also /guild/create) are internally used urls.
I believe /guild/create is how CeeAitch created a guild named "Dystopia+", because CREATEGUILD sanitizes input.
I tried a lot of parameters but it always returns Failure...