Cooperative missions in Factions are different from their equivalent in Prophecies. In Prophecies players complete a main mission and an optional bonus mission. Cooperative missions are easy to avoid in Prophecies as most areas are accessible without completing missions. Factions makes all missions compulsory for accessing new areas and completing the game. The bonus mission has been removed and replaced with a three-tiered reward system. Some missions' tiers are based on the time taken to complete the mission, others are based on completion of extra objectives (such as keeping a certain number of NPCs alive until the end). Gold, experience and a skill point are given at each reward tier. Several new concepts for co-operative missions have been introduced, such as missions with two teams of eight and missions specifically for killing a single boss.