The Silent Realm Guardians wouldn't have been as scary if they could talk. If they had just a couple lines of monologue they wouldn't have seemed anywhere near as scary because as long as they don't, the Silent Realm Guardians are just killing machines that stop at nothing to find you. (I don't know what they do after that because I've never been caught before.) When they can talk, they're no longer killing machines but characters in the game with thoughts and feelings and they don't seem as scary.
XD I laughed when I saw Fledge's name on the list! Anyways, I voted for Demise since his appearance gets to me whenever I battle against him, despite of the number of times I have already beat him. His appearance just makes me cringe every once in a while.
1. Their presentation. When they wake up, that music plays and their eyes glow. Very intimidating.
2. No defense against them. The only thing you can do is run.
3. One hit and its over. Insta-kills are generally intimidating and this technically counts.
Seriously, these guys are incredibly intimidating.