Challenge Mission

From the Factions FAQ:

Cooperative missions involve specific scoring objectives, such as holding out against progressive waves of enemies. The rewards may be experience, gold, and faction, depending on completion and mission. You will see personal bests and high scores displayed within the game.

Guild Wars Factions features the following challenge missions:
 * Dragon's Throat (Kaineng City)
 * Altrumm Ruins (Echovald Forest, awarding Kurzick faction)
 * Zos Shivros Channel (Jade Sea, awarding Luxon faction)
 * Amatz Basin (Echovald Forest, awarding Kurzick faction)