ADOM had similar issues. You kill a cat any time, you miss out on a later quest. Instead you just had to fight the cat lord. Missed out on a very powerful ring.

And it was so, so easy to kill a cat. You use the automatic repeat-move key and auto-hit when you collide with a monster, and if you ever find a cat anywhere that way, its dead. People would rage-quit and start all over, it was that frustrating.