Another background about mindcontrol!
Dominated Will
Rare
You were the victim of mental domination from some powerful entity or spellcaster. But, due to some twist of fate, your would-be master is well out of reach from you, and most likely forever. Yet still you feel some overwhelming compulsion to carry out their will.
Choose two ability boosts. One must be Constitution or Intelligence, and one is a free ability boost.
You are trained in Deception and Lore related to your master (such as Vampire Lore if your master is a vampire).
You are permanently under the effects of mental domination, forcing you to pursue a general but directed objective. How you pursue this goal is up to you, but you must take reasonable steps to see it carried out. The exact objective is up to you and the GM; examples might be 'undermine the authorities of the land to better prepare for my conquest' or 'gather wealth to fill my treasure troves'. Objectives should generally be tailored so that they do not immediately conflict with the goals of the party while still creating potential for internal or interpersonal conflict in the future. You are unaware of your mental domination, and explain any course of action taken in pursuit of your objective as a lapse of judgement, simple happenstance or a choice done of your own free will, even if that explanation is illogical, contradictory or nonsensical.
Your GM may occasionally force you to follow a single non-suicidal course of action that aligns with this objective. You must attempt a DC 11 flat check, or DC 5 if the compulsion directly contradicts one of your anathema. An anathema that would directly prohibit your entire objective does not reduce DCs; your dedication to that anathema was worn down long ago.
Critical Success You refuse the compulsion and cannot be compelled again for 1 week.
Success You refuse the compulsion, and cannot be forced to take that particular action for 1 day.
Failure You immediately obey the compulsion. You continue to pursue the course of action for 1 hour, until you have completed a finite compulsion, or until the compulsion becomes self-destructive.
You gain the Vacant Stare reaction. Whenever you are compelled to complete a course of action towards your objective, your uses of Vacant Stare resets.
Vacant Stare [reaction] (Fortune, Mental); Frequency once per day; Trigger You fail or critically fail against an effect with the Mental trait Effect Your will is already in the grip of someone else. You become partially catatonic in response to a new source of mental manipulation. Reroll the triggering save. After resolving this second save, you become stupefied for 2 rounds.
Running this Background as a GM
This background has the potential to create possibly disruptive or difficult situations for not only the player who has taken this background, but fellow players as well and for you. It is extremely important that both you and the player interested in this background come to a good understand of what is or isn't acceptable as a command, as well as what actions are okay in order to fulfill that command. It is also important to gauge this with the rest of the players that will have to play in a game with this character.
While the background should remain a mystery to the in-world characters, it is best to establish boundaries with all participating players as to what is acceptable for this background, even if at the expense of losing some of the mystery behind what is happening. You can maintain some of the mystery by establishing what isn't acceptable rather than what is, but you should still be careful to avoid any commands that would be disruptive towards the progression of the narrative, cohesion of the party, and to the overall enjoyment of the game. Consider what reactions could occur to an action if the character is caught in the act.
Forcing the dominated character to rob a minor NPC in a town the group is passing through may be less disruptive if the consequences of that action may take some time before they catch up with the character, such as suddenly finding themself a wanted criminal in the county or the group as a whole suddenly on the run from local authorities (and hopefully in a way that keeps the story moving forward and the group from holding too much animosity towards the dominated character).
Forcing that same character to rob their fellow party members is often going to result in conflict that could result in the narrative grinding to a complete stand still, or the group splintering apart in a way that makes the players enjoy the experience less, or the player that chose this background to regret their decision.
If you cannot come to a good understanding of how to run this background, it would be best to suggest that they take a more fitting background instead and work on alternatives.
Edit: Included some suggestions from others and some guidance for GMs due to the potentially disruptive nature of the background.