How well do you know Black Metal? (Part 1: Proto-Black Metal / First Wave)

Let's start with the ones who coined the term "Black Metal" in the first place - Venom. While usually not considered Black Metal themselves (or First Wave Black Metal at most), they did pave the way for the genre. Already many typical Black Metal elements were present in Venom - Satanic lyrics and edgy pseudonyms, for example.
What were the pseudonyms of the band (at the time of their first demo tape from 1980, Demon)?

And what TV show intro did Venom get the riff for their song "Countess Bathory" from?

Another one of those that "only" paved the way is Mercyful Fate. Even though their sound is really far from what is considered Black Metal, their lyrical themes aren't. It's a lot of Satan, and evil. Besides, they were more "authentic" than Venom with the whole Satan-business because their lead singer, King Diamond, also actually considers himself a Satanist (even though a boring LaVeyan one).
So, what was King Diamond's microphone stand made out of?

Another bone-related Mercyful Fate story is that of Melissa, a human skull King Diamond got from his younger brother. King Diamond not only named the skull and imagined a backstory to it, but also consequently named a Mercyful Fate album after it. The music video to a King Diamond song was also filmed at the very cliffs where Melissa was initially found - but which song was that?

Let's move onto harsher territories - Bathory. I don't really need to tell you about Bathory. Everyone should know about Bathory. Screw you if you don't know about Bathory.
When did the three founding members meet?

And what was the name of the compilation that was released even before Bathory's debut album and featured two Bathory songs, which appeared on there mostly thanks to personal connections of the band?

Now, another band that pushed the boundaries of Metal and thereby inspired the sound of following Black Metal bands... You guessed it, Hellhammer! (You probably actually didn't guess that) Their aggressive and extreme sound, not to mention their low production quality, made them a harshly criticized band during the early 80s when they were active - only to be celebrated as forerunners of the Black Metal genre years later, when that kind of music really started to take off.
What's the reason Tom G. Warrior - founder, vocalist and guitarist of Hellhammer - pushed the band to have such a dark sound?

And what naturally follows from Hellhammer? Right, Celtic Frost, the band born from Hellhammer's ashes, with a new concept and a somewhat more professional sound.
The band's name "Celtic Frost" was chosen for several reasons. First of all, it didn't sound like a typical 80s Metal band name, and the band didn't want to be limited to the Metal genre. Also, the band's members do have a Celtic background. But what other reason was there for naming the band "Celtic Frost"? (which, by the way, is pronounced with a hard c - I was right all along, Miro)

And which Celtic Frost album did Tom G. Warrior call the "hugest mistake of his entire life"?

Last but not least, let's talk about another one of Black Metal's inspirations - Thrash Metal. Only Thrash Metal with particularly high aggression and Satanic lyrical themes, that is. Early stuff from Slayer or Sarcófago comes to mind, for example. But what trio of bands had, according to Black Metal musicians like Fenriz, Apollyon and Euronymous, also a big impact on Black Metal with their early releases?