Abyss of Time

The Abyss of Time is an massive underground labyrinth that appeared in the playable epilogue in Persona 3: FES, titled The Answer. Originally a state of hibernation, it became 'active' when it was attracted by the grief and sorrow of SEES, and spread it's influence there, rooting down below the dorm.

Historical Information
When the phenomena of Dark Hour and Tartarus was created, Tatarus, growing out of the ground each night eventually left a great cove underneath it's roots. Following the death of the Protagonist, the Abyss of Time was attracted by SEES' grief and sorrow, and and spread it's influence there, rooting down below the dorm. Eventually the Abyss of Time would become active, locking SEES in an infinite time loop where the time will re-reset itself whenever the clock hits 12:00 P.M. ,leaving the time forever froze in March 31st.

The Answer
Following the events of the Protagonist' death, Mitsuru Kirijo decides to shut down the dorm, while calling the remaining SEES members to regroup one last time prior separating their paths. During the celebration, they found out that they are locked in an infinite loop where the day kept staying in March 31st. As their confusions arise, SEES was attacked by Metis, an anti-shadow weapon who claims to be Aegis' sister.

Eventually Metis was subdued, and from Metis SEES learned about the phenomena of the Abyss of Time. Metis first subject to destroy SEES, so the Abyss of Time can be neutralized, as she believed that they are the main problem of the existence of the Abyss of Time. SEES would later decide to take on their Evokers one last time again, to investigate the Abyss of Time.

Throughout their investigation, they encounter a recurring silhouette resembling the Protagonist, but upon reaching near him, the silhouette flees, leaving powerful Shadows to halt SEES' advance.