As a video editor, I have access to numerous sound banks for the projects I work on.
While browsing through the animals sounds, I heard the sound the spiders make.

The source of the spider's sound is a cat purr. :blink:

Upon hearing this, I keep listening to other sounds and find other Daggerfall sounds. Seems like I was browsing through the same sound bank the Daggerfall team used.

The sound the mummies make is that of a "Big Cat" as titled by the company.
The Giant Scorpions are also in the cat category..

Remember the man that guards Daggerfall's Castle doors? The one to whom you must get the permission to enter? Good, now remember that he makes some sort of a "Uhhhmm" sound?
Well the source of that is a Tiger, but they lowered the pitch.

The Vampires (Not the Ancients) is a "Female Groan".

I'll need to keep looking in that sound bank for other sources.
I was very, very surprised when I heard the mummies in my head phones and saw it titled "Big Cat"

these sounds have been used in lots of games & movies, 'stock' sounds

Indeed, but what surprised me was the source of the sound vs their usage.
A cat purr for a spider
A "Big Cat" for a mummy.

The two sounds I'll always remember because I keep hearing them in most medieval movies are the door opening sounds. The one for the regular doors and the one that plays as a background sound in a dungeon.

Indeed, but what surprised me was the source of the sound vs their usage. A cat purr for a spider...A "Big Cat" for a mummy.

That's what they're called, not necessarily what they are.

Are they derived from these sources or just named as such? Either way, it's interesting...

I suspect that some or many were derived from the source of the name, but, possibly/probably, some of them were synthetic, but named for whatever the creator thought they sounded like..

I am pretty sure that spider sound IS a sampled cat purr.. Sounds like it to me. Probably a mic that was actually touching the cat's abdomen used to record it, but I think it's valid.

I'm kind of wondering what power tool was used for the werewolves.. *lol* Sounds like a chainsaw to me. That female vampire groan is always a surprise when you haven't heard it for ages (just ran across my first one, since restarting the game THIS decade, a couple days ago. Freaky!)