We need to create a tag for the original character, invented by the Guchiyama artist. Original character name: 異形の魔女. Can be translated in various ways, such as "atypical witch" or "unusual witch", and one of the fan translations of the manga has adapted the character's name as "The Tenebrous Witch".

Which option would you choose? Or leave the Japanese pronunciation "Igyō no majo" altogether?

I know in a few tags with Japanese characters, they keep the original Japanese name. However, I do not know how easy it would be for English speaking fans to find it, so if the most popular translation is the fan translation, I would say it would be better to use that one.

Besides, if an official translation ever comes out, we can always have it re-aliased to an official version of the name without too much difficulty.

ok, i think i will use a variant from the not very high quality, but the most popular translation of the manga, at least for now. thx for answering.

I would rather go with the romaji route, you keep the "original name" while at the same time making it readable for non-japanese. Think of "Shingeki no Kyojin"(or better known as "Attack on Titan") as an example, which would be literally translated to something like "Attack's Big Person" or "Attack's Giant", which doesn't sound that good, so that's why I would suggest sticking to the romaji name until an official translation is found, this is specially true when it comes to name with japanese origins, since many of the names in japanese are not actual names (as we know them) but rather words, like cherry, fox, wall, wind, etc. But then again, that's just my opinion.

From Jisho:

1. fantastic; grotesque; strange-looking; suspicious-looking

If you wanted to go for a direct translation, "Grotesque" would be the most fitting.

For now, I'd say just set up a Bulk Update Request and use whichever one sounds most fitting. The BUR can be shuffled to whichever people prefer.

We actually already know her name.
It's given as 「ニール」 in the Japanese script, and on Twitter the artist uses Nihil in English replies.
The guy is ダグラス (Douglas).