Quakera is a magic spell in Final Fantasy VII Rebirth. It is granted by either 
Petrify Materia or Poison and Petrify Materia. It is the mid-tier petrifying spell above 
Quake and below Quaga. Quakera inflicts strong non-elemental damage, as well as inflicting the 
Petrify status to one enemy.
Use[]
Quakera can be cast when either petrify or poison and petrify materia is equipped. The spell deals strong non-elemental damage on its own, albeit with a high MP cost compared to its peers. It also inflicts the petrify status, a very dangerous status to a foe that causes them to turn to stone if they receive enough damage during the status.
Quakera's ability to deal non-elemental damage means it is a good way of inflicting damage against enemies that resist elements but not magic damage itself. It may be more efficient and more effective to cast the spell of the element the enemy is weak to if an enemy has an elemental weakness. In other causes, Quakera is a solid choice especially until Comet is available.
Quakera can be amplified by some 
Support Materia. Both HP Absorption Materia and MP Absorption Materia can increase a party member's sustainability when using the spell. Magic Focus Materia can increase the spell's damage, and Magnify Materia can make for a powerful combination when it hits all enemies at once. Magic Efficiency Materia can alleviate its high MP cost, and Swiftcast Materia can shorten its cast time, though there are better beneficiaries for these materia.
Using Quakera with Aerith's Arcane Ward will cast it twice. Further using Yuffie with Doppelganger when in Arcane Ward can cast Quakera four times, potentially overwhelming enemies.