Unbeknownst to the two factions, the wars are masterminded by Shinryu and Cid of the Lufaine, so that each time a faction wins the survivors are killed and everyone is revived to begin a new war. Cid wanted to refine Chaos into the ultimate weapon to take back to his original homeworld and seek vengeance on Onrac, the government that destroyed his family, while Shinryu would absorb the warriors' memories and experiences and become stronger.
There have been twenty cycles seen or alluded to in the two games.
1st to 11th cycles Edit
Cosmos and her warriors lost all these cycles. During the second cycle, three warriors are said to be unable to withstand purification, and are not summoned again. It is unknown who they were. The Warrior of Light appeared in an early cycle, Shantotto and Gabranth left the world through portals to the Rift, and Prishe disappeared forever after Garland defeated Cosmos. It is unknown if this is the second cycle, or a different one.
12th cycle Edit
The main story of Dissidia 012 Final Fantasy, where many of Cosmos' warriors fail to stop the infestation of manikins, which is why Shinryu did not revive them in the next cycle. At this time, soldiers from both sides were transferred to the opposing group.
13th cycle Edit
The main story of Dissidia Final Fantasy, as well as the bonus chapter of Dissidia 012 Final Fantasy. In this cycle, several Chaos and Cosmos warriors have switched sides while Cid feels guilty and has rebelled against Shinryu. At the end of this war, the Cosmos side wins and the heroes return to their respective worlds by Cid possessing Chaos to teleport them away.
End of the Cycle Edit
Here ends the war of the gods. Destiny's hand cannot be stayed.
The thirteenth is the final end of the cycle, as supported by the secret reports and character info on Cosmos, Shinryu, Cid, and Chaos. Shinryu absorbed Chaos's experiences for its own and fled to the Rift. Cid of the Lufaine, released from his prison in Scenario 000, reunites with Cosmos (revived by the power of the warriors' crystals).
Nightmare World Cycles Edit
The following cycles only take place in the nightmare world Cid is placed in during the thirteenth cycle.
14th to 18th cycles Edit
Because of Cid's actions, the pact with Shinryu was broken and the dragon sought vengeance for being robbed of the power, experiences and memories of the summoned warriors. Shinryu forged a pact with Chaos, and sealed Cid in a nightmarish alternate world where the war didn't end in the thirteenth cycle, Chaos survived, and the war continued until the twentieth cycle.
In this reality, Cosmos has never won and Chaos's power continues to grow from the discord and destruction of the endless war. After the eighteenth cycle, Chaos is overcome by the power. His mind breaks and he descends into insanity, becoming Feral Chaos. He wipes out all of the Warriors of Cosmos at the beginning of the cycle, and turns on his own warriors in his madness.
The Warrior of Light, the only warrior born in World B, met his death at the hands of Feral Chaos, being the last warrior standing in protection of Cosmos.
19th cycle Edit
During this cycle, Shinryu has accumulated enough knowledge and strength from the wars and evolved into his final form, called Shinryu Verus. Little else is known about this cycle.
20th cycle Edit
At the start of the twentieth cycle, Feral Chaos attempted to slay Cosmos but she had lost the power to summon warriors, so Cid took the form of a moogle and rescued her from Order's Sanctuary, sealing her in the Cavern of the Earth near Melmond, where Chaos would be unable to reach her. Denied his victim, Feral Chaos challenges Shinryu. Cid seals the northern continent to ensure the conflict between Shinryu and Chaos is contained, and seals himself into the Cavern of Earth with Cosmos.
It is implied the Confessions of the Creator scenario is the aftermath of the twentieth cycle. The world is devoid of life apart from moogles and the manikins, although there exist spectres of long since defeated Warriors of Cosmos. When the player finds Cid, as the "mured moogle", he is alone, and it is unknown what happened to Cosmos. In musing upon how the player party arrived in the nightmare reality, Cid theorizes they were unintentionally summoned by him, as neither Chaos nor Cosmos is in a position to summon warriors. Once Feral Chaos is defeated, he regains his sanity and thanks the player party for freeing his father, and the nightmare reality is broken.
The following is a list of the warriors and which cycles they participated in. Though no cycles before the twelfth are named, the knowledge that the more someone fights the more memories they regain allow an approximation of when they likely appeared in the cycle by judging how much they remember of their own worlds. The warriors are listed in chronological order of their original games in the Final Fantasy series.
The Warrior of Light's cycle of entry is unknown, but was an early one. Garland was present in the cycle from the beginning, being summoned by Cid to serve as Chaos's right hand.
Firion may or may not have participated in cycles before the twelfth, as he has few memories and needs the wild rose to stir them. If Firion participated in earlier cycles, it was not many, for his memories are sparse. The Emperor has been in many cycles, including at least one where Garland, Gabranth, Shantotto, and Prishe were present, as seen in an official quest.
The Onion Knight's cycle of entry, like Firion's, was likely just before the twelfth cycle or the twelfth cycle itself, as he cannot remember his own name. It is unknown when the Cloud of Darkness entered the cycle, as she indicates she knows the "legend" of the Onion Knight warrior in the thirteenth, but no indications of the lengths of her memory are given otherwise.
Cecil appears to have been summoned for the first time in the twelfth cycle, but regained his memories of Kain and Golbez during that cycle. Kain is stated in Yuna's museum profile to have participated in the cycles as long as she and Jecht have, indicating he has been through many cycles, and has thus regained many of his memories of home. Golbez remembers Cecil and Kain and has other memories of their home, but it is not made clear if he remembers as much as Kain, so he may have participated in as many cycles as Kain has or not, but has certainly been through several.
Bartz's museum profile states he does not have vivid memories of his past, but he remembers Galuf, though not by name, and so likely participated in at least one cycle before the twelfth. Exdeath's museum profile states he has recovered most of his memories, including those of Bartz and Gilgamesh, so he has been in many cycles. Gilgamesh, as an outsider to the cycles, may have stumbled into them countless times and thus has maintained all of his memories since he was not officially summoned. He was present in at least one early cycle where he sparred with Prishe.
Terra likely participated in a cycle prior to the twelfth, as she knows about airships during that cycle, and in the thirteenth tells Cecil she has some memories of war and battle from her world. Kefka could have taken part in any number of cycles, as there are no indications of any memories he has or has not recovered. Kefka had enslaved Terra arguably before the twelfth cycle, knowing full-hand what she is capable of.
Cloud took part in several cycles, having regained many of his memories. Tifa was summoned for the first and only time in the twelfth cycle, so she has not regained any of her memories except for those of Zangan. It is ambiguous which cycles, if any, Sephiroth participated in prior to the twelfth, as he does not fully remember Cloud or Tifa, and only remembers the Lifestream and Jenova after fighting them. He thus has few memories of home, and so it is likely that he only took part in a handful of cycles prior to the twelfth.
Squall was present in at least one cycle prior to the twelfth, as in an official quest during that cycle, Cloud alludes to he and Squall meeting in a past cycle. Squall is aware in the thirteenth cycle that Ultimecia is his destined opponent, indicating he remembers her from his world. He also remembers Rinoa toward the end of that cycle. It is unknown how many cycles in which Laguna participated, as he doesn't remember Squall or indicate any other memories of home. However, it is unlikely Laguna would remember Squall no matter how long he fought, as this Laguna is the younger one from Final Fantasy VIII's flashbacks, and thus would not know Squall. Ultimecia has been through "many" cycles, as stated by her museum profile.
Zidane is stated in his museum profile to have regained many of his memories, so he has taken part in several cycles. The same can be said of Kuja, who, by the time of the twelfth cycle, is bored with the fighting, and the two are initially on friendly terms, showing they remember each other (and likely mended fences at the end of the events of Final Fantasy IX).
Tidus was a new warrior in the twelfth cycle, and thus has no memories of home, save for his name and his hatred of Jecht. Yuna and Jecht have both been through many cycles and remember much about their home world, including each other, Tidus, and Yuna's pilgrimage. However, Yuna tells Tidus that she doesn't remember everything yet.
Shantotto and Prishe were summoned in one of the earliest cycles. It is ambiguous which specific cycle they vanished, but during their time, they regained many of their memories of each other, with Prishe even remembering her pet name for Shantotto.
Vaan may have taken part in cycles prior to the twelfth, or may have been newly summoned during that cycle. He indicates several times he has knowledge of airships and is fascinated with them, but there are no hints of any other memories he has recovered. Gabranth was one of the earlier participants in the cycle, and though the exact cycle is unknown, he vanished from the war around the same approximate time as Shantotto and Prishe. In a battle with Shantotto, he alludes to fighting her in a previous cycle, so Gabranth has been through at least two cycles. In an official quest where the two meet, neither Vaan nor Gabranth indicate they know the other, but as Gabranth was dismissive of Vaan's presence in Final Fantasy XII, he may not have acknowledged remembering him.
Lightning has few memories of home and, like Firion, has them stirred by the presence of his wild rose. During the twelfth cycle, she uses the term "Primarch" when speaking to the Warrior of Light, indicating she remembers the Sanctum. She battles Exdeath and, as a result, recovers her memory of l'Cie and fal'Cie, but does not use the specific terms, so she may be newly summoned in the twelfth cycle or have only taken part in a few cycles prior. It should be noted that in Dissidia Duodecim Prologus Final Fantasy, Lightning narrated to the player about herself being a servant of the gods, "That's what I found myself, when the goddess of harmony called upon me." It is unknown whether she was narrating about the twelfth cycle only or narrating about the greater conflict in general in the introducing narration to Dissidia Duodecim Prologus Final Fantasy. If the latter is the case, then she was summoned in the twelfth cycle.
In addition to the above, it is mentioned in Report 14 that there was a warrior in an early cycle who possessed a powerful mind that puzzled Cid, leaving him to wonder if the warrior was connected to Shinryu. It is mentioned that at the end of an early cycle, three warriors were so severely weakened they perished upon being purified by Shinryu. It is unknown who these unnamed warriors were, or which god they served. This could refer to the cycle in which Prishe vanished when Cosmos was killed, but it is uncertain.