The War of the Spider was a conflict between the fledgling undead army of the Lich King and the Nerubian Empire of Azjol-Nerub in Northrend. The war began when the spider-lords sent their elite forces to attack the Icecrown. The Nerubians were immune to the Lich King's Plague of Undeath and powers of mental domination, so in the following ten years the Nerubians fought with a strong and effective guerilla-tactic which the Lich King could hardly battle against. After that ten years Ner'zhul and his dreadlords won by invading their subterranean capital Azjol-Nerub with enormous mass of undead and the cunning Nathrezim, destroying the crypts and tunnels of the spider empire.