Ekplixi
I think that Wilhelm might be Lucifer, but X Cube thinks he's Odin. There are lots of different bits of evidence towards either theory, so...
Wilhelm is still confusing me about exactly what mythical figure he's representing (if it's a mythical figure at all), since all of the characters are refferencing
something it's doubtful that'd they'd just leave Wilhelm out of the whole symbolism thing.
Now one thought I had, probably only due to the fact that we just finished a unit on WWI in history, was that maybe Wilhelm is a refference to Kaiser Wilhelm of Germany - now I don't know enough about the Kaiser to say much other than that they share both a name and a seat of power.
Again with the name connections, one of the brothers Grimm was named Wilhelm (if I'm not mistaken, google isn't infalible) - it doesn't seem like a very big connection until you concider the only (that I know of - I haven't seen any others yet) allusion to the brothers Grimm was in the story of Marienkind - which I'm not going to go into in depth since I already have another topic about it, but basically it has to do with equating the 13 doors of heaven to the 13 zohar emulators, etc. Again not a whole lot to support this theory, but it's an interesting thought.
Though probably of more note than the previous two, Nietzsche's full name is Friedrich
Wilhelm Nietzsche. Seeing as how each episode has been titled after a work by Nietzsche and how [really minor ep 2 spoiler] Wilhelm quotes Nietzsche at the end of ep 2 maybe Wilhelm is a refference to Nietzche himself - or that could just be one aspect of the symbolism around him.
And lastly with my name tangent, the etemology of the name Wilhelm, from behindthename.com: "...Wilhelm, which was composed of the elements wil 'will, desire' and helm 'helmet, protection'." The most interesting component is probably "Wil" concidering that Wilhelm makes at least one comment regarding someone's will during the game, especially if you concider his line: "His will shines with such wondrous light. It's a shame to relegate him to such a minor role." maybe that's where the "helm" - "protection" comes in and that might make him the protector of wills (is there a mythological figure with a similar role? I haven't found it yet but I haven't been looking for very long). Eh, I'm just typing this as I go so I haven't really thoroughly thought out any of this yet, but hopefully someone'll be able to make some sense of it.