Troll Patrol: Throwing Down

Clever...$b$bJust when it seemed we were getting things under control, they tunneled right underneath us and secured the shrine!$b$bNow we're caught between two nethurbian armies and our predicament is worsening by the minute.$b$bAs our first course of action, we must stop them from reinforcing. Their tunnels must be sealed.$b$bTake these grenades and throw them down their craters to the northwest.