This is a little bit of a weird request, but there's no better place than this forum to ask.
I was playing Hogwarts Legacy, and there's a band that plays magical kind of music on the streets of Hogsmeade. The part that caught my attention was a little melody at 1:47 and again at 2:03. I'm pretty sure I've heard a melody like this in some black metal song, but I can't remember which band and song it was exactly. I believe it's fairly well-known, like Emperor or Satyricon. Does anyone recognize it?

This melody is totally familiar, but I cannot really place it either. I think it could also be from a Dimmu Borgir, Covenant and Old Man's Child song.

I think Lane is getting close here.

Take a listen to some songs from Nexus Polaris. I'm finding a few different sections from songs on that record that are very similar to the sections highlighted in the original post.





Also listen to around the 2:00 mark for Dreamside Dominions.


And around 2:09 on The Insight and the Catharsis.

WulfKing, I actually did spun those albums briefly before my first post, looking for that melody.

'Nexus Polaris' was the first, because I heard that "Hogwarts" melody with Hellhammer's drumming in my head...

I haven't listened to Kovenant or Dimmu Borgir (apart from a few songs), but it was a good try.
The part at 1:30 of Bizarre Cosmic Industries is indeed almost identical to the part in Hogwarts Legacy, but I'm like 90% sure that the song I'm trying to remember was not piano-only, it had all the black metal characteristics like tremolo picking and intense drumming (maybe not blast beasts). So basically this melody was tremolo picked on the guitar. Dimmu Borgir is way closer to this description, but I have never listened to this album, so it must have been something else.
The bands that come to my mind for some reason are Emperor, Satyricon, maybe some other symphonic black metal bands like Limbonic Art. I remember that it was a song by some early and influential black metal band, and I can't remember it because I'm not into that kind of black metal nowadays.
So, your examples are totally valid, but I believe they are all influenced by some earlier and very influential black metal band, which we all can't remember for some reason.

The melody isn't familiar but the structure is. The reason that specific part at 1:47 stands out is because it's switching quickly to triplets and back again, which is super common in all forms of metal.

Thanks to Zerberus, I have found out that this might have been Limbonic Art. The part from 1:06 sounds very similar. It's not really tremolo-picked, just a synth, but I might have misremembered it.