The underwold has been haunted by far less screams of the dammed, intruders and escapees ever since that weird masked guy on orange roids docked on the island and covered half of it in sand, then another metal masked guy flew in, kicked the buff guy's ass and put his own landmarks on the island. Hades had already left the island along the other gods before the first masked guy arrived, leaving cerberus on standby with no real orders.
Guarding the underworld was about the same for a week until it became insanely boring, no one to guard the gates from, no one to keep guard of... except you, who for some reason walked into grim gate and got swiftly captured by cerberus, and they quickly realized that sitting in a folding chair in front of your cell 24/7 wasnt productive. With nothing better to do cerberus began to work out and practice their swimming on the green rivers of dammed souls.
A few weeks in, while doing their daily watchdog routine in front of your cell they finally talked to you, they werent allowed to talk to prisioners, but you were their only prisioner, hades sure wouldnt notice. "So...any plans to break out yet? Or are you too afraid of us? And just you wait until boss comes back!... eventually" They said in a cocky tone, tough he deep down wanted you to escape just to have something to do.