A #Borderlands Unified Theory based on existing game Elements, a Thread if you will: Part One The Proving Grounds are simulations of the original Trials that were used to determine who would receive Siren powers from the Eridians. There are Six Trials. There are Six Sirens.

#Borderlands Unified Theory Part Two: Sirens were created to defend against creatures the Eridians unleashed into the Borderlands universe by breaching the phase dimension, so they could focus on other things, hence the Proving Grounds.

#Borderlands Unified Theory Part Three: The Sirens proved to be too independent and powerful, and to keep them from becoming threats, the Eridians created obedient synthetic life to defend their technology & a prison for them, Kairos.

#Borderlands Unified Theory Part Four: The Eridians continued to experiment with creating subservient creatures powerful enough to defend their technologies from Cosmic entities they'd encountering traversing the Phase Dimension, but none could match the Destroyer.

#Borderlands Unified Theory Part Five: Realizing the immensity of the threat the Eridians reach out to the Sirens of a new generation, who are unaware of their origins, and work with them to buidl the Great Machine of Nekrotafeyo & construct & seal Elpis & Pandora.

#Borderlands Unified Theory Part Six: Guardians go on to honor the orders of their creators, which set them against Sirens from the beginning. Sirens, still ignorant of their origins find themselves drawn to each other & the Vaults their predecessors were anointed to protect.

#Borderlands Unified Theory Part Seven: The Phase spanning both space & time allowed those with access to it, and Vaults, which exist outside of temporal space, to place things within them that may have information, or even power culled from another point in the past of future.

#Borderlands Unified Theory Part Eight: Three key examples are the Artifact within Eleeser protected by the Sentinel that reveals the Vault of the Warrior, and as such the importance of Pandora. Then there are the Eridian Resonator & Analyzer on Promethea & Pandora respectively.

#Borderlands Unified Theory Part Nine: Each Artifact connects past, present, & future knowledge, creating temporal predestination by influencing the recipients of that foreknowledge. Borderlands 4 brings that full circle with the Vault at the End of Time, & its contents.

#Borderlands Unified Theory Part Ten: Borderlands The Presequel introduces precognition. Borderlands 3 introduces foreknowledge of causality, which created the previously unprecedented precognition. Borderlands 4 introduces the Phase as a means to transcend temporal limits.

#Borderlands Unified Theory Part Eleven: The Great War as set up by Borderlands 3 and 4 pits the Gaurdians against the Sirens with what appears to be a Universe locked in a perpetual loop of destruction and rebirth. Arjay speaks of seeing the "First Star" during his final rant.

#Borderlands Unified Theory Part Twelve: The Destroyer consumed stars & threatened to blackout the Heavens. Tyrene aspired to be the Only Star in the Sky & consume the power of the Destroyer. Ultimately, we witness that darkness of a starless universe, & a Phoenix relighting it.

#Borderlands Unified Theory Fin: The Order synths constantly speak of causality repeating, as if time is locked in a loop that they have been programmed to uphold. The Seer spoke of Acausalities who threaten the preordained chronology. The Great War may be to write/rewrite Time.