Goor (quest not available)
Type: level 60/3 Howler
Location: roaming the eastern parts of Mount of Hero South, usually near the small Mine entrances
Tactic: Extremly bugged due almost constant being in retreat mode and thus being unhitable most of the time. Bring healing and lots of patience and expect to kill up to a dozen wild-life on the way. The poisons are nasty bug nothing too serious with good regenfood and dodging.

Perrefin Sadirn (quest not available)
Type: level 60/3 Ghost
Location: spawnable via using a monolith at the northwestern edge of the Scoured Hills
Tactic: Mix of strong melee and magic attacks, including a blood hook. But very doable at the level if you keep an eye on your healing / resistbuff and dodge a bit.

Possibly Missing
It seems like every Zone has two menances in it. Based on that information, we still miss:
Scoured Hills - one (possibly bugged)