Quintessa's History
Early life
Being a ruler of Cybertron alongside the other Creators, Quintessa builds herself up to become a seemingly benevolent figure for the Cybetronians and that she plans to destroy their ancient enemy, the notorious giant planet eater Unicron. However, twelve Cybertronian Knights learn that she is not what they seemed to be and that she plans to drain energy from Earth to restore Cybertron with a machine utilized by a powerful staff, as Quintessa believes that the Earth is nothing more than the dormant body of Unicron. Unwilling to let the life on Earth suffer from the Creators' wrath, the Cybertronian Knights rebelled against Quintessa. They stole the technology before hiding it away on Earth and branded her as a deceiver, much to Quintessa's fury.
Transformers: Age of Extinction
Qunitessa does not appear in the film, but she and the other Creators are mentioned by Lockdown, who was sent by Quintessa to capture Optimus while all Transformers (both Autobots and Decepticons) are being hunted down by the world authorities due to the Chicago incident caused by Optimus' former mentor Sentinel Prime. However, Lockdown and his conspirator Harold Attinger end up being killed by Optimus, who decides to travel to outer space to confront the Creators in order to spare the Earth from the Creators' wrath.
Transformers: The Last Knight
Quintessa made her first appearance in the film after hearing of Lockdown's death. Deciding to take matters into her own hands, Quintessa uses the space bridge technology to transport herself, her soldiers (known as the Infernocons), and the dead planet Cybertron to Earth. Upon Cybertron's arrival on Earth's orbit, a comatose Optimus Prime crash-lands into Cybertron, awakening from his stasis. Awaiting Optimus' arrival, Quintessa has Optimus chained and berates him for his war against the Decepticons before using her magic to brainwash Optimus into doing her bidding. With that in mind, Quintessa dubs Optimus as "Nemesis Prime" and orders him to destroy Earth, saying that it's the dormant body of Unicron.
As the plot goes, Cade Yeager and a young girl named Izabella (who was orphaned during Sentinel Prime's attack on Chicago) learned of the ancient Cybertronian technology that existed on Earth ever since medieval times, and that it was located in the bottom of the ocean. They also learned that the ancient staff (hidden by the Cybertronian Knights during King Arthur's reign) can be used to activate the technology, and that Quintessa plans to use it to revive Cybertron by colliding it into Earth. After the Autobots locate the staff before engaging into a fight with the Cybertronian Knights, Optimus (having followed them in secret) managed to steal the staff and fly off just as the machine arises from the ocean. During the battle on the machine, Optimus attempts to kill Bumblebee, who eventually managed to snap Optimus out of his trance. Unfortunately, Megatron managed to steal the staff from Optimus and formed a deal with Quintessa to revive Cybertron so that the Decepticons and Creators can rule it, as Quintessa anticipated that Optimus would break free from her control.
The Autobots then team up with the Cybertronian Knights to fight against the Decepticons and Infernocons, right before they used Lockdown's ship to stop the collision on Earth. Following the deaths of many Decepticons and Infernocons, Optimus was able to finish off Megatron by sending him off flying back to Earth, but Quintessa uses her magic to restrain Optimus, angrily swearing to kill him for ruining her plans. However, Quintessa is seemingly destroyed by Bumblebee while Viviane deactivates the machine by removing the staff from it, saving both Cybertron and Earth from colliding with each other.
In the end, the Autobots return to rebuild Cybertron as it is now in orbit with Earth, but they are unaware that Quintessa has survived her encounter with Bumblebee and has taken refuge in Earth. Disguised as a human, Quintessa meets with a group of scientists who have discovered a giant ancient spike (which happens to be a part of Unicron). She tells the scientists not to touch the spike, saying that he does not like it. Quintessa then says that she can tell them how to destroy the planet eater (Unicron). After that, she starts to show her true form. It is unknown what happened to her afterwards, though it's likely that she revealed who Unicron was, and possibly his past as well.
