Stalker

The Stalker can follow one player during the night. In the morning, the Stalker will get a report telling them who their target visited last night.

Role Type

The Stalker is free to choose the same target multiple nights in a row.
The Vampire's Familiar has a nightly ability identical to the Stalker. These roles also receive the same morning report.
The Stalker cannot observe some (parts of) abilities that are used on (living) players. These are the Djinn-swap and the target to which a Succubus redirects another player. So if a Djinn is stalked no visit is reported, and if a Succubus is stalked, the Succubus is only seen visiting the person they're redirecting, not the person they're redirecting to.
Roles that "visit themselves" are not seen by the Stalker. These include: the Messiah, the Tarot Reader, and the Shapeshifter. The Protector and Shaman can visit themselves if they use their defensive ability on themselves. It is also possible for a Succubus to redirect someone to themselves, making them appear self-visiting.
If the Stalker targets the 'killing wolf' they will get a report their target visited the person who died in the night. All other Wolfpack members are not necessarily seen visiting this target (it is still possible for Wolfpack members to be seen visiting the same/another player because of abilities they have used). For an explanation of how the Wolfpack's kill system works, see the corresponding section in the Factions page.

As a Stalker, you can see players visiting other players. This tells you that they have a certain role, although you cannot be sure which role they have. So your information is usually only a starting point for further investigation.
Once you've shared your report(s), the people that you've stalked can now explain why they were seen visiting. In addition, players can compare your information with their own - they might be able to tie the visit to other events in the game and so create a better image of other players' identities.
You have to consider whether/when it is wise to share your information, and how much of your information you want to share. Sometimes, it may be better to only share only a portion of your information, and not all of it, at once. Your information may expose important village members to the evil faction(s). On the other hand, you may force your enemies to account for their visit(s), meaning they have to come up with some story that can be verified by the village.
If you see that someone has visited a player who died the same night, you cannot be sure that this person actually killed the deceased player. But it is still likely, and usually this is a good moment for you to speak up!