Telepaths and empaths won't be able to detect much of anything from the tunnels, as they're only a construct of the dream and not a real living thing. They may be able to sense an overwhelming amount of negative emotion coming from any nightmares they encounter, however, and may also be able to sense that they are in a collective dream rather than the physical world. We'll leave it up to your discretion!

Empathetic Pokémon in particular will be instinctively more protective of their Trainers and more guarded than usual.