Angelo has the power to see what he refers to as spirits, although he's not quite sure that's the correct term for them. To the majority of people, these spirits are completely invisible, but for Angelo they appear as amorphous floating blobs that seem to have no single solid form. The spirits are not intelligent, and do not have any drives or personalities of their own, doing nothing if not given instructions. They are relatively common, and seem to be more plentiful where there is more signs of human life. In the city there might be several in a single room, while in a forest he'll only see one every so often.
Angelo is capable of controlling them to a limited extent, and primarily uses them to observe. He can instruct a spirit to go elsewhere and then report back, or else check in with them later. The spirits are not tangible, cannot interact with the environment, and can only observe as a human would have. However, since they're invisible and can pass easily through walls, they make the perfect spies. Angelo is capable of having as many watchers as he'd like, and can freely ask questions about what they saw or heard, which they will answer him truthfully. Their ability to retain knowledge seems short, and past a few hours the spirit is likely to have forgotten the original instruction entirely, meaning they have no utility for long term spying. The spirits do not talk, but instead simply pass information directly to Angelo when he is nearby.
