Go to the south, to the rise where the Troll camps are found. As quickly as you can attack a Troll; get it down to at least 75% health then use the Collar. This will make the troll friendly and fill him with a hate for Stone Guardians. He will quickly reorient and head down to the castle gate to attack the guardian. Now grab some more trolls! You should be able to gather 4 or 5 trolls before they drop the first guardian. Now follow them up the hill. Above the castle is a grove with 6 icons (2 of each). Help your Trolls but there IS a time limit. The whole hate thing only last 5 minutes or so. You should have just enough time to dash in and get the 3rd icon as they attack the Guardian there, then run down the hill and back to the Sentry Station.