Mind flayer

Mind flayers and master mind flayers, represented by the letter h, are especially perilous monsters, capable of eating your brain, resulting in feeling stupid, or perishing as your last thought fades away... Wearing a helmet will protect against this, and their corpses make you smarter if you eat them.

They can sense your presence remotely, and you theirs.

They make excellent pets, as they make quick work of shopkeepers, and their telepathic outreach is then soothing.