Faith (フェイス, Feisu?) is a recurring positive status effect in the Final Fantasy series. If a character has the Faith status, they will usually get a boost to their Magic Power, though this is a bit more complicated in Final Fantasy Tactics.
Appearances
Final Fantasy IV
Faith doubles the party's magic power. It is cast via Twincast with Rydia and Cecil, or Rydia and Rosa, or via Recall.
The Toad-Faith glitch in the 3D Remake is activated by casting the spell Toad on a character or the party outside of battle, which will grant Faith status to the characters or party for the next battle only.
Final Fantasy VII Rebirth
Faith boosts a target's 
Magic Attack by 20% for around 30 seconds without weapon skills or accessories that lengthen status duration. It can be applied by the 
Faith spell from the 
Empowerment Materia and by Sonic Boom from 
Enemy Skill Materia. It is opposed to Defaith, each removing the other.
Final Fantasy XII
Faith increases the affected's magickal damage 30% and their magickal healing by 50%. Characters under Faith are also more successful in inflicting targets with negative status effects. Faith status is bestowed by the spell of the same name, from being hit with the Rod of Faith, and from wielding the Wyrmhero Blade.
Final Fantasy XII: Revenant Wings
Faith is a positive status effect that raises a unit's Magick Attack. Penelo's Mystic Dance and the Judge of Wings's Heroism are a few of the spells that may grant this effect.
Final Fantasy XIII
Faith raises Magic by 40%, affecting damage from abilities such as Fire, Ruin, Deprotect, and Last Resort. It has an upgraded version, Faithra, which increases Magic by 80%.
Final Fantasy XIII-2
Faith raises Magic by 75%. It can be bestowed by Faith and its area-of-effect version, Faithga. It can also be bestowed by several Feral Links; Buccaboo Ace's Spirit Infusion, Circuitron and Cloudburst's Friendly Fire, Nabaat's Sadistic Surge (depending on Paradigm Pack's role composition), Gahongas and Yakshini's Fanatical Dance, and Mewmao's Precious Prayer.
Lightning Returns: Final Fantasy XIII
Faith raises Magic by 50%.
Final Fantasy Tactics
While under Faith, a unit is treated as if they have maximum (100) Faith points without inflicting the consequence of raising the permanent faith statistic too high, which would cause the unit to leave party after the fight. This can be positive or negative as it raises spellcasting ability, but also raises the effect of spells cast on that unit. The opposite of the status Faith is Atheist. Faith lasts for 32 ticks.
The mystic's Belief and templar's Faith can grant this status, and the rod of faith weapon will grant the unit Auto-Faith status.
Final Fantasy: The 4 Heroes of Light
Several abilities give a boost to a character's magic power. The Musician's Nocturne boosts magic power for three turns, the spell Magick works similarly, and the spell Lux gives the status permanently. The Black Mage's abilities also raise magic power in a similar fashion, but they only work for one turn. The boost effect does not stack.
