A ghost is a user that is not linked to an email address. Like regular users, ghosts belong to a group, participate in matches, are ranked, have activities and rewards. The ghost's name and icon can be edited only by the group's admin.
Ghosts allow an admin to manage groups with a mixed crowd of users, some of which are linked to an email address while some (i.e. the ghosts) are not.
Later, a ghost user can always be linked to an email address (via the webapp) and converted into a regular user.