Random Last Knight canon now that I have the DVD:
Quintessa is, in fact, a servant of Unicron. Her goal in draining him with the Staff was not to kill him and restore Cybertron as she said, but to transfer his consciousness into Cybertron, simultaneously giving him a new body, and killing his rival, Primus. Her other story was a lie. In fact, she lies a lot, hence her eventual title of "the Deceiver." She also relies on minions to do the heavy lifting because, aside from her mind-control powers and the ability to reformat Transformers, she isn't actually very strong, and could go down easily in battle.
Also a lie: Being a Prime. We already met the original seven in ROTF, and she isn't one of them. She showed up on Cybertron sometime after their extinction, when their memory had faded to legend among the populace, claiming to be a Prime, able to exert enough influence to gain her own team of Guardian Knights, out of Iacon, in a time when they were common. Her end goal was to convince said guardians to come with her to Earth to drain the planet, but over time, they wound up seeing through her scheme. Some of them stole her staff and spirited it away to Earth, hiding it where it was least expected, and standing guard over it, while another group managed to seal her away far beneath Cybertron, along with her Infernocon guards, and went into stasis there.
They remained forgotten beneath the planet, until the events of DOTM torn the planet to pieces, unleashing her, and her Infernocon guards. The guardian knights on Cybertron were destroyed, save for a single one, who wound up taking a slow, sublight trip to Earth in a ruined ship, with the Talisman in his possession, while Quintessa went to work with her minions, lashing the planet together, and setting it on an even slower path to Earth.
At some point, Quintessa realized she'd need at least one new Knight to finish the job when she came to Earth, and so hired Lockdown to bring a Prime to her. Lockdown's explanations to Optimus in AOE about the Creators and mixing species were more of her lies. (I haven't decided where the Seed came from, though. Maybe Quintessa got one from somewhere)
Lockdown failed, but fortuitously, Galvatron would arrive on Cybertron himself, having immediately stolen the piece of Lockdown's ship the Autobots were using in AOE and headed to Cybertron, intending to ambush Optimus when he landed, since he figured he'd be heading there at some point.
Quintessa would recreate him into Megatron, shaping his body into her ideal Guardian Knight, brand him, and feed him more lies and ego trips (She chose me because I am stronger!), before sending him off to Earth to do what she'd wanted Optimus to do, find the staff. Optimus would, of course, arrive later, and lo and behold, she had two knights.
(I came up with a whole story around Megatron/Galvatron earlier in the thread. This could work with that, except he'd show up on Cybertron as Megatron already, and just be branded).
Edited by Fear or Courage, 30 October 2017 - 09:15 AM.