Firaga is a magic spell in Final Fantasy VII Rebirth. It is granted by either 
Fire Materia or Fire and Ice Materia, and is the highest-tier 
Fire-elemental spell above 
Fire and Fira. Firaga deals great fire-elemental damage, with a high MP cost and long casting time, and costs two ATB charges. The spell fires a flame projectile that homes in on the targeted enemy.
It is also used against the player by the following enemies: Bashfulisk, Diabolic Variant, Hecteyes, Irasceros, and Ironclad.
Use[]
Firaga costs 21 MP to cast with a level 3 fire or fire and ice materia equipped. The spell is effective generally at damage output, but its prohibitive MP cost and ATB charge use means it should be used seldomly, and should ideally be used only against enemies weak to fire (particularly humanoids and plants) unless no other spellcasting option of its caliber is available. Among its peers— Blizzaga, Thundaga, and Aeroga—Firaga's strength is in being able to deal area-of-effect damage instantly.
Firaga outclasses both Fire and Fira in terms of damage output. In many situations however, players will prefer to cast Fira if there are no two ATB charges available. Firaga is best used against enemies already staggered or otherwise immobile (such as after casting Stop or Sleep).
Using 
Support Materia can alleviate some of Firaga's shortcomings and make it safer to regularly cast. Swiftcast Materia in particular can mostly eliminate its costly cast time, while Magic Efficiency Materia reduces its prohibitive MP cost. Otherwise, HP Absorption Materia and MP Absorption Materia are effective pairings to improve a party member's sustainability, Magic Focus Materia can increase its damage, and Magnify Materia can be a powerful way to hit multiple enemies at once with immense damage; this can be especially helpful in the Hard Mode flower-picking odd job in the Grasslands Region against the numerous plant monsters. 
ATB Boost Materia can get the caster to two ATB charges quickly when they need to use the spell.
In some cases, players may wish to bolster Firaga with two support materia. This can be done by equipping two fire materia (or one fire and one fire and ice materia) and pairing each up with a support materia. Swiftcast, for example, is effective when used alongside magnify or HP absorption, as is magic efficiency alongside MP absorption.
Using Firaga with Aerith's Arcane Ward will cast it twice. Further using Yuffie with Doppelganger when in Arcane Ward can cast Fira four times, potentially overwhelming enemies.
If the party member casting Firaga has unlocked their fire-elemental weapon ability (e.g. Heatwave for Aerith), Firaga becomes Firaga α, which will bestow a fire-elemental sphere to the spellcaster for the rest of the battle (unless the player changes the element with Blizzaga α etc.) that will supplement small magical fire-elemental damage when defending against certain enemy attacks (perfect-blocking not needed) and when using ATB abilities. The attacks from the "fire sphere" do build stagger and can be critical hits.