Watchers are ghost-like creatures that appear exclusively in the various Silent Realms. Like Guardians, they cannot be hurt.
The purpose of the Watchers is to patrol the silent realm and alert the Guardians if an intruder (you) is found. There are two types of Watchers.
Sky Watchers float high above and generally do not stray from their patrol path. If you’re caught in their spotlight, the Guardians will be activated and you’ll need to collect a Sacred Tear ASAP to stop them.
Earth Watchers float near the ground and are deceptively hard to outmaneuver. These also have a patrol path, but if you step into the outer, wider faded spotlight (around the bright central spotlight), they will chase you until they catch you (activating the Guardians) or you leave the faded spotlight.
When they’re chasing you, you’ll hear a constant jingling sound. If you have plenty of stamina, you can dash to try and shake them off. Otherwise, if there’s a tear nearby, you can let them catch you and then touch the tear (but don’t do it the other way round, because they won’t stop chasing you).