In mission 17 Kel'Thuzad, the reborn Lich, need to speak with the mysterious demon lord, who have issued the plans so far. But to do that, the both heroes need to secure a demon gate to communicate with the lord. As the demon gates are favorite ground of orcs to play, they need to dispose of some orc champions. With the help of the Frost Wyrms, it should not be a problem. The Frost Wyrm is the strongest flying unit of the Scourge. It attacks both ground and flying units with a powerful damage, and can freeze buildings and towers.