A Gate of Idramm is a rune that can call a powerful demon. The rune is used primarily for destruction and is one of the most dangerous runes of the Tortallan Universe. Akhnan ibn Nazzir tried to draw a Gate of Idramm and would have completed it if Faithful hadn't gotten Alanna to stop him. If he had completed it, it's possible that it would've destroyed the entire Great Southern Desert, not just the Bloody Hawk village.