Mallus wasn't the only demon that escaped his prison.
The Giantess Periboea escaped from the Underworld and plans to plunge the known world into chaos.
The Legends, with the Olympians' blessing, are the only ones capable of stopping her.
But the gods are stubborn and the Legends must first earn that blessing.
General disclaimers:
A) I do not own DC's Legends of Tomorrow. Obviously.
B) Everything up to and including "Witch Hunt" is canon and has happened before the start of this story.
C) I will not take most of season four into account (again, only up to "Witch Hunt"), for the simple reason that season three just finished when I started planning the story. So Wally will appear, but Charlie will not.
D) I started planning for, and outlining this story in late August/early September. Evidently, season four had not aired yet. Should, by any chance, Greek monsters show up that the show also used… I decided to use them before I even had the chance to see them come alive on the small screen.
E) I did watch season four while I wrote the first draft (starting in November) and am currently still revising. If any monsters are the same, I stuck to my original plan, though it is possible the show might influence their appearance/behavioral patterns in my writing.
F) You do not need to know everything about Greek mythology to understand this story; everything will be explained thoroughly whenever something shows up in the story. Still, feel free to look up some extra information if you'd like.
That was all. Now sit back, relax and enjoy the show.
When the earth shook, the Giantess Periboea did not let it distract her. After all, she resided in the Underworld – the ground regularly shook and in this prison, nobody ever paid much attention to the shaking anyway. The inmates dismissed it as another trivial thing; another time Poseidon became angry, Hephaestus let a volcano blow or someone had tried to escape.
Periboea had not known the world for a long time. As soon as her father and uncles had been born from Gaea, their mother – Mother Earth – they were sent to Mount Olympus to kills the gods and replace them. Their plans to rule the world were thwarted by the Olympians, who killed every Giant that rose against them. The Giants were sent to Tartarus – a literal Hell, where the worst of the worst ended up in death. Other than a brief glance at a blue and green world, Periboea only knew red and brown, hellfire and shadows.
The ground did not stop shaking. Other inmates pointed at Poseidon throwing a tantrum, but Periboea did not believe this. Poseidon's earthquakes were different – they were regular and its tremors could be felt when she placed her hand on the hot rock wall keeping everyone inside Tartarus. These tremors continued for way too long to be Poseidon's and she could feel them in her bones; something that had not happened before.
Something big – something wrong – was going on.
Periboea was right. As soon as the tremors stopped, their prison guards flew around in a frenzy and kept a closer eye on everyone than they would have done before. The inmates – Giants, monsters, and evil human souls alike – grew uneasy. It was only inevitable a riot broke out. The Titan Cronus started it, demanding to be set free, and everyone's attention was fixed on him, his followers and their struggle at the gates of Tartarus.
Nobody was paying attention to Periboea when she noticed a crack in the red rock wall. As she approached it, she found it was big enough to allow for someone of her posture to squeeze through. Despite what her name may suggest, the Giants were trapped in human-size forms so they would better fit in and were more easily manageable. In this state, with her small posture, she had a chance to escape.
The Giantess turned her head to the gigantic crowd. Her father, Eurymedon, was talking to some of her uncles, Alcyoneus, Clytius, and Mimas. Another uncle, Ephialtes, supported Cronus and attacked the guards. With one look on them, Periboea decided to leave them behind. They would draw too much attention to her and would proclaim the escape route to everyone who wanted to hear. She did not want them to jeopardize her chances of escaping.
When she was certain nobody looked, she climbed into the crack, pushing and squeezing herself deeper and deeper. It did not give her any extra room as she progressed, but it did not grow smaller either. She forced herself to keep moving, out of fear the prison guards would follow her.
They could not follow her here. They were too big to fit in the crack and could only seal it to make sure nobody else could pass. Periboea was free of Tartarus! She only needed to push through.
After what felt like an eternal uphill climb, a small ray of sunlight broke the darkness. Half an hour later, Periboea exited the crack and lay on the grass. She was exhausted from the effort and laughed like a small girl. It did not matter that the sun nearly blinded her and that the texture of grass that was not barren was strange to her. She finally saw the blue and green world she had only seen once. And she was happy.
Periboea did not stay in the Greek meadow for too long. The guards were going to notice the one female Giantess was missing. They were going to look for her and take her back to that hellhole. For now, she had to be content with passing for a human and staying in that tiny human form for the time being. When she was strong enough again, Periboea would be able to grow to her original size again, but that had to wait.
Periboea walked away from the crack she'd crawled out of and grinned. The world was beautiful, yes, but the Olympians were still in charge. Her fathers and uncles had taught her they had been horrible and the world needed the Giants.
The Giantess would continue what her father and uncles started and unlike them, she would succeed. She would bring Destruction to Mount Olympus and kill the gods. She would free her uncles and rule and kill anyone who opposed her, and anyone who prevented her from reaching her life-long goal.