Geas

A Geas is a temporary curse that binds the cursed person into servitude to do an objective. The objective is usually a short quest or task, but can be a long one depending on the caster. While under a Geas the creature can not think or do much of anything else besides the quest. If they try to resist the Geas it can cause them much harm varying from not being able to rest by nightmares to intensive pain until they take up the quest again.

The Geas is removed once the task is completed and can be removed magically if done correctly. When one puts a Geas upon a creature they might even do it to a group to ensure that the task will be completed if it is a long quest.