Ouch, that's pretty nasty...

Ah yes, I had forgotten about that one...
Caught me out a few times in the past.

As r-k says, the danger system relies in part on calculating the next monster to throw at the player based on number of moves required to make a kill, which relies in turn on HP and equipment. So it's kind of delicately balanced and so difficulty to make changes without inventing a new game.

On a related note, there's a PR up to fix the occurrence of powerful zombie spawns: https://github.com/Attnam/ivan/pull/295

Scary. Did she pick up and equip the amulet, or did she spawn with it?

You could try going into wizmode and press * and print the character danger values. If its danger value is similar to other characters in the catacombs then it will spawn when expected.
When I did this I noticed the danger values for various undead configurations were all over the place, probably the reason those powerful zombies keep appearing...

It's cool, I didn't pick it up before, and I didn't properly realise the significance of the IgnoreDanger flag till now. We can always switch it back, ready for next release.

The reason goblin berzerkers are appearing early is because IgnoreDanger is set to true. Everywhere IgnoreDanger is used, an HP and Day requirement for generation needs to be specified. You'll notice that low hp creatures like floating eyes etc, use this feature because they wouldn't have enough stats to generate normally by the danger system. Check out proto.cpp for more details.

Horns check for creatures in a square around the player. Kenny must be beside you, because for any empty square around the player, it creates a piece of fruit. You're inside the loop that checks for creatures, that's why you have seven pieces of fruit.

I found where the change was caused all this: https://github.com/Attnam/ivan/commit/586ecc0322967034c63844...

It seems like a bit of exuberance on red's part

I looked it up and it's similar to the vampire bat. Just add this line for the bone puppy in char.dat:

AllowedDungeons = { 2, XINROCH_TOMB, ATTNAM; }

and it should appear in either Xinroch's Tomb or the Attnamese Catacombs