Yeah, I think Fauna Lore would be the most sensible for even a lot of what we'd call "Monsters". After that it really get into specifics. I would tend to tell players if something is commonly known of they'll likely be able to identify it (i.e. if there are Ogres and Trolls in the world) even if, for most people, they are scary tales told to keep the children from wondering off too far. Either the tales were based on some truth or they'll never see the non-existent creature. You could make it fairly easy and say anything not supernatural is 'normal'. So Ogres and Trolls would be normal if they are known of and covered under Fauna Lore.
So, what we would term "legends" or stories might tell people what a Manticore is. It just depends on how well known they would be in your setting. Aside from that you're wanting information on something that is very unusual or pretty much unheard of... and that's where I'd get into Undead Lore, Demon Lore, Xeno Lores, etc.
Let me give an example, and I"m going to be somewhat vague due to spoilers for possible group members. Dragons exist in my world. People know tales are told about them and know what they are supposed to look like, but it's very, very rare that a person would have seen one. The most educated the individual the more they might believe they actually exist. So, the knowledge of legends of dragons, and what they look like would cause most of the population to know what they were facing if they actually saw one... but the specifics of them, where they tend to live, how they tend to live, their general traits, etc would be Dragon Lore knowledge. Their social structure, attitudes/outlook on the world, actual known locations, would be very usual knowledge (i.e. first or second hand direct knowledge).
