I haven't gotten all that many characters to the Cat Lord level, and most of them have killed one cat (so I can quietly walk by)e.

I had a wizard reach the Cat Lord level, actually eligible for the Ring!! I was pretty pleased, since I think I only actually got the ring with one prior character. There was a tension room, though, of Ancient Karmic Dragons. I was Magic Missile-ing them, when one panicked and ran down a hallway.

I didn't particularly want a panicked Ancient Karmic Dragon potentially multi-attacking me around a corner. So, I cast one Magic Missile down that hallway...........

You focus your magical energies to release the spell.
The ancient karmic dragon is hit by the magic missile!
The cat lord is hit by the magic missile!
The cat lord seems to shrug off the missile!
The cat lord roars in anger!

...so I guess he had stepped into view, or popped back into visibility, in the same turn that the dragon started to run away. Bye bye, ring!