To clarify NO MAGIC means no magic. No inexplicable occurrences. Chi manipulation is not to be used like the force in Star Wars. No demonic possession causing your character to suddenly be capable of inhuman feats.

Initially the allowance of mysticism was to open up the possibilities for diversity in SDL. But in no way was that to encourage the use of paranormal abilities. A dueller can say "My sword is holy and has been blessed by kami-sama", however a dueller may not actually perform supernatural feats with the sword. In this case the sword may have some kind of mystical nature however it remains only hearsay and conjecture to add a bit of flavour to the character's background. NOT in anyway to be used as a device to over come enemies beyond a psychological standpoint.

In the case of Voodoo, the idea of it is allowed to a degree, but don't expect to win matches by sticking dolls with pins. Voodoo is like a documented religion. Just like Christianity had its miracles, Voodoo also had its own unexplained phenomena. However, like religious miracles, such happenings are considered paranormal, not something that can just be done and replicated each time one faces an opponent.

One may argue that these regulations on magic are rather limiting. But it is these regulations that make the world of SDL a rich and cohesive environment to work in. There is still much room for creativity without magic, as proven by those who have worked around the limitations.

So what can you do in SDL? As stated before you may suggest that your character have some mystical item/quality. However clear it up in your profile information that it is merely a story.

Example 1: Demonic possession.
There are characters in the sdl who believe they or an item they own is possessed by a demon, they may talk to themselves/the item, or hear voices or have a split personality and suddenly become more violent when they believe they are under the influence of the "demon". But there is to be no actual demon nor any supernatural powers to go with it.

Example 2: Magical items.
A character may claim to own a magical items that blesses them in some way with such and such abilities. But it is to remain a claim only.

Example 3: Extra human traits.
An OC may be a mutant to a degree. Disproportionate body parts, extra fingers, warty growths that resemble lizard's skin etc. Though try not to push this too far, we don't want to see X-men in SDL.

In addition to the NO MAGIC rule, High tech gadgetry is also out of the question. During the feudal era, the only guns available were flintlocks. So no revolvers or contraptions that wouldn't have existed back then. Also when it comes to science fiction, be sensible, if there is something we couldn't even achieve today, don't expect to to be possible back in the 1500s.

Just remember that there are a lot of people who have tried working around the rules, so trying to make a non magical, magic character wont be as original and outlandish as you might think. Use your common sense when designing your OC, if you know your ideas would cause concern then perhaps you need to rethink things and find an alternate way of making your OC interesting.