Re-opened: A FemPercy and DC crossover Fanfic Sequel to Old Wounds

Chapter 1: A Monster's Birthplace

DISCLAIMER: All rights and characters belong to DC comics/universe Warner Bros. Young Justice and Rick Riordan.
Percy's POV
3 years. 3 years since it had all began. 3 years since it had all ended. 3 years since I had lost my sanity. It was ironic. 3 - an ancient number. There were 3 fates. The big three. 3 demigods per quest. 3. It was a sacred number. One that cost my life.
"SCCCAAARRRRPPPP" metal hit metal.
"PIT" my foot tapped the sulfuric ground.
"WWWHHHHOOOOO" I exhaled in the poisonous air.
Everything around me was designed to kill. To torture. To imprison. Everything was a weapon. I was a weapon. If I wasn't, I wouldn't be down here in Tartarus. The gods had outcast me when I stood up to them. They threw me into a torturous land beyond the gods. I almost hadn't survived at first. I was starved, dehydrated, and half - dead. My will was gone. I walked for miles and miles on end. My clothes turned to rags, my mouth felt aflame. It was indeed Hades. But I grew stronger - faster - smarter - more powerful. I did everything I could to survive. My fatal flaw was gone. And my humanity had all but ceased. I continued like this for almost a year. But then, I came across Tartarus himself. Upon sight, we immediately engaged into a battle. We fought for days. But in the end, we came to a stalemate. Tartarus was shocked that a mere demigod, one that barely escaped him in the first place, grew to be an equal. So, he took me in. It was an uneasy alliance. We both were always on high alert for any murder attempts. Yet over time, he became a sort of father figure. He was far from perfect, but so was I. The lands that once were my worst nightmare became my home. And over time, Tartarus let me into his heart too. For almost 2 years, we lived in peace together. He became my family, and I his. We would spar, and he would teach me all there is too know about the mythical world. It was a dream, but a nightmare to anyone else. It was the most peaceful my life had ever been, despite living in Hades.  But that had all changed when I had gotten a message.  A message from the world above.  A message from the gods.  For almost 4 months, they started pestering me with letters; errands they need me to run for them.  And each time, I wanted those letters burn with a raging passion.  I had changed; adapted to survive.  Never again would I be restrained by the bounds the gods had put upon me. 
"SCCCCAAAARRRRPPPPP" metal hit metal again.
I analyzed my workmanship.   It looked just like Luke's sword - Backbiter.  Almost a perfect replica, almost.  Standing, I slashed around with it a few times.  It was perfectly balanced, sharp too. 
"Epizon" I muttered.
It meant survivor in Greek.  A perfect sword for an exiled hero.  But I didn't think of myself as a hero.  Nor did I see myself as a villain.  No.  I was just a person trying to endure the weight of the world. 
"Hello Percy," Tartarus greeted.
His voice echoed throughout the endless space.
"Hello Tartarus," I responded.
I was relaxed.  I felt no hostility towards him.  But I still kept my guard up - always.  I only trusted him as far as Arion could run.  In the mythical world, the number one rule is don't trust anybody.
"You have another message," he stated.
He held out the letter for me to take.  I nodded, sheathing my sword with reluctantance.  Taking the letter from Tartarus, I walked away opening it.
Dear Percy,
I know the gods wronged you.  And I know we wronged you too.  But a new threat has  arisen and we desperately need your help.  I have dispatched one of the legions to investigate the threat, but I fear the worst.  There has been rumors and sightings.  Nature is on a rampage.  People are disappearing and many are found dead.  And it isn't just the mythological world that is being affected, it's the mortal world too.  Percy please, we need your help.  I understand if you don't want to help us.  The gods banished you to Tartarus for Pluto's sake!  But don't do it for the gods, do it for Grover.  At first, I thought Gaea was rising again, but I soon found that it was Grover.  He's gone insane.  He killed Chiron Percy.  So help or don't help.  I thought you would just want to know.  If you do decide to help, Nico will be waiting for you at the entrance to the underworld.  If you don't decide to help, I fear I might be seeing you soon.
                        Respectfully,
                      Praetor Reyna
P.S. This is Thalia, SEAWEED BRAIN! IF YOU DON'T COME UP HERE TO HELP, I WILL PERSONALLY GO DOWN THERE, RIP YOUR HEART OUT AND SHOVE IT DOWN YOUR THROAT FOR DISAPPEARING FOR 3 YEARS AND LETTING GROVER BECOME A PSYCHOPATH!
                                     Love,
                                   Thalia
After reading the letter, I watched it burn in the kindling flame. The shriveled up and turned to ash.  I had no loyalty to anyone anymore.  If anything, I'm rooting for Grover to continue defying the gods.  I glanced around, Tartarus was gone.  I smirked.  I wasn't going to help, but that didn't mean I didn't want to see what would happen.  Checking the sword at my side, and checking the hanging pen I wore as a necklace on my neck, I started toward the underworld.  I wonder how Death Breath has been handling, well, being dead.
Hey guys, I wish I could've updated more, but I ran out of time, I'll probably update this again next weekend and possibly tomorrow.  Also, I hope you like it so far!  It's just the beginning of this sequel.  See you on the other side! (Literally in this story)