Alvin’s arc across Riders of Berk is a slow-burn siege. He doesn't attack with a fleet; he attacks with spies, sabotage, and psychological warfare. He steals the Dragon Manual . He captures Mildew (the village's crotchety anti-dragon elder). He nearly marries Stoick’s betrothed. Mark Hamill’s performance gives Alvin a greasy, intelligent menace that makes him feel more dangerous than any dragon.