It's the Get Four Rocks In A Row To Win game.
It's kind of like Connect 4 but not enough to bother involving lawyers.
Play against anyone else on your realm who also has Four Rocks In A Row installed.
Solo play not yet supported.
Use any of the following commands to start a new game :
/friar
/friar [OpponentName]
/4riar
/4riar [OpponentName]
/c4
/c4 [OpponentName]