Aliasing walpurgis_no_yoru_(madoka_magica) -> walpurgisnacht_(madoka_magica).

Reason: Walpurgisnacht is the original German name, and it's pretty clear that it's what's meant. "no yoru" is basically a direct translation to make it more accessible for the Japanese viewer.

The official website actually uses the English "Night" in the glossary link, so I think I would prefer walpurgis_night_(madoka_magica)

But the original concept is called Walpurgisnacht, and we default to using the original language's names where possible.

I'm with Hazuki on this one, though it's pretty much a judgement call here.

FWIW, when I was translating some Madoka comics, I instinctively went with "Walpurgisnacht". Personally, I don't really care either way, but yeah...

Probably any of the three is fine, but did the alias as suggested.