Mutually Exclusive Quests are quests in Xenoblade Chronicles where one quest is associated to a second quest and the party will complete one option or the other. Indeed, the party will complete one quest and the second will disappear or only one of both will be triggered, so both quests cannot be completed, that's why they are mutually exclusive.
A mutually exclusive quest can be triggered with its corresponding one and the party has to chose which one to complete. However a mutually exclusive quest can also be triggered without its corresponding one after having completed a previous quest while one of two possible routes had to be chosen, or after having chosen one Colony 6 Immigrant amongst two possible candidates; therefore the proposed quest will depend on the chosen previous route or the chosen immigrant. In general, two corresponding mutually exclusive quests are triggered in the same area, except four of them that occur in two different areas.
There are 50 Mutually Exclusive Quests; 18 of them are Timed Quests. Four mutually exclusive quests are triggered in different areas, there are two Alcamoth Quests mutually exclusive with one Eryth Sea Quest and one Valak Mountain Quest.
= Timed Quest