Final Fantasy VII is home to some of the series' most memorable lore and stories, to the point where it has started being retold for a new generation of players. Among the established narrative are plenty of fan theories about connections between certain characters and enemies. One of these theories positions the Knights of the Round summon as related to the lost Cetra civilization that defeated Jenova in an age past. Here's a breakdown of the theory that Final Fantasy VII's most powerful summon are the spirits of Jenova's first adversaries.
The Last Stand of the Cetra
First, some background on Jenova and the Cetra makes understanding some of the details a little less daunting. The Cetra were a nomadic and spiritual race of people, established long before humans, who were attuned with the planet. The Cetra were unique in their ability to commune with the planet itself, tapping into and guiding the Lifestream's flow to create fertile lands. Some 2000 years before the events of Final Fantasy VII, an evil alien entity crash-landed via meteorite on the planet's northern continent. The entity, later named Jenova, would bring the Cetra to their knees.
Jenova sought to destroy all life on the planet, then use it as a vessel to travel the universe in search of another target. The entity approached the Cetra and through a virus (believed to be the genetic material of Jenova itself) that would turn the wise beings into monsters. This effectively wiped out the majority of the Cetra, leaving only a handful left to combat the alien threat. The survivors banded together, set on stopping the calamity before it conquered the planet.
The remaining Cetra were able to contain Jenova by sealing the entity away in the North crater, the impact site of the meteorite carrying the creature. Jenova would remain undisturbed for thousands of years until the Shinra Power Electrical Company excavated the site while searching for remnants of the Cetra civilization.
Ancient Saviors?
The theory revolves around some interesting reactions in the game's code when fighting against the Jenova-SYNTHESIS boss that preludes the more memorable fights against Sephiroth. If the player uses the Knights of the Round summon during the Jenova-SYNTHESIS encounter, it triggers a massive increase in health for the next two bosses. Bizarro-Sephiroth receives an additional 60,000 HP and Safer-Sephiroth gets an extra 80,000 HP.
Some fans believe this interaction is a hint that Jenova and the Knights of the Round summon are connected in some way. The most logical connection? That they were the small band of Cetra warriors who succeeded in defeating and trapping Jenova in North Crater. Furthermore, fans have elaborated that it's not implausible to believe that, upon death, the Cetra warriors returned to the Lifestream and were reborn in the form of this Materia to protect the planet should Jenova ever return
Unrelated Entities
The main issue with this theory is that a lot of information is assumed and based on a single interaction. It's interesting that using the Knights of the Round summon on Jenova causes something to happen during the following two bosses, but nothing ties the two together narratively. It seems just as likely that the summon triggers increased boss health due to how powerful Knights of the Round is. If the player uses the Materia to one-shot Jenova-SYNTHESIS, they'll probably use it to make their fights against Sephiroth more manageable.
Yoshinori Kitase, the title's director, had responded to this theory in particular. He'd said that, when Tetsuya Nomura created the summons, none of them "have any background story attached to them." He followed up by saying, "That makes it difficult because if you think about it that way, we might have to make it that way." Kitase seemed to hint that it's not impossible for the team to make this theory a reality in Final Fantasy VII Remake. Until then, it's a question of whether you believe the Cetra transcended death to combat their mightiest foe.