Enthrallment

Enthrall or Mind Control is a recurring concept within the Final Fantasy series. It refers to the enslavement of a character, typically either a villain or playable character, by an evil power in order to do their bidding. With respect to the villains, it is typically not known to the player that they are actually puppets of another evil power until the story develops. The term does not refer to willing servants, but rather to an individual whose mind has been forfeited or has been otherwise strongly compelled to enter into servitude.

Final Fantasy IV
Multiple times in the story, Cain betrays the party in order to serve his new master, Golbez, whom after the incident at Mist Village had apparently placed him under a spell to enthrall him.

Golbez is revealed to have been enthralled all along, having been a pawn of Zemus in order to activate the Giant of Babil.

Final Fantasy VII


All Sephiroth Clones, including Cloud Strife, are subject to the will of Sephiroth and Jenova, especially with regard to the Reunion. Cloud is temporarily subjected to servitude to Sephiroth twice - once at the Temple of the Ancients, and again at the Promised Land, in both cases being made to hand over the Black Materia.

Final Fantasy VIII
In Disc 2, it becomes evident that Edea's malevolent actions are not willful, nor do they comport with her kindly demeanor back when Squall, Quistis, Zell, Irvine, Selphie, and Seifer were in her care as children. She reveals that as a Sorceress, her powers and mind were subjected to the will of Ultimecia, who used Ellone's powers to junction herself with sorceresses from the past. When aboard the Lunar Base, Rinoa comes out of a comatose state, only to be posessed by Ultimecia and free Adel from her tomb.

Later, as part of Laguna Loire's plan to assassinate Ultimecia, Adel and Rinoa are once again possessed by Ultimecia in order to accomplish Time Compression.

Final Fantasy XIII
While they are not mentally possessed, L'Cie, regular human beings, are enthralled by the Fal'Cie, god-like creatures with great power, to do their bidding, on pain of turning into Cie'th - mindless beasts who roam about for eternity in torment.