The hunter will monitor a list of target players.
It will then look at their activities at a regular interval and make a graph out of it.
You can then look at the graph and visualize when is the player online or offline, and identify their playing hours.
You can add a player to the hunter list by visiting the galaxy page, click on a player, then click the "Add to hunter list" button.
Warning: This feature is CPU intensive. You should keep this list fairly small.