On your way to the Quarry to rescue Simon, you will pass the river with two sprites flying around it. At this point it is crucial that you record the Will o' the Wisp. After you cross it, Jared will sense something but ignores it. Then you will see the River Troll wake up. After you escape with Simon and return to the River, the River Troll will block your way. The only way to cross is to make it sleep by feeding it ten Goblins. Keep using the Will o' Wisp you caught earlier to lure the Goblins to the River Troll. You must do this every time you cross the river unless you turn it into stone. To do this, you have to use Simon's Splattergun to push it towards the sunlight. When it is out of the shade, an intermission sequence will start, and it turns to stone.