Gehenna And Tartarus

Long had the Mother of Chimeras lived in peace upon the the mountain which now bears her species' name.  She prayed upon the fauna and ate the flora as any other beast, content in living a simple life.  Gehenna birthed and raised generations of her children upon that mountain.  For the most part, her kind was peaceful, avoiding humans if possible, but defending themselves if need be.  Of course, there was always one or two bad apples in the barrel.  And all it ever takes to ruin any reputation is a single slight.  Thus did the neighboring kingdom of Lycia come to fear the Daughter of Echidna.  When the boy Bellerophon was sent by Proetus, King Iobates saw an opportunity to rid his people of the beast.  Thus did he task the young man with slaying the Chimera, in part to punish him without angering the Erinyes of the Underworld (who punish those who murder their guests) and would benefit if he somehow managed to slay the creature.  
For his part, the boy was terrified at the seemingly impossible task put before him.  He could not go back on his word, but he would die if he tried to slay Gehenna.  So he went to the man Polyeidos, a 'seer' from Corinth.  Of course, the man wasn't actually a seer, but a mortal agent of the Olympians.  Seeing the boy's distress and receiving approval from the great Athena, Polyeidos gifted Bellerophon with a golden bridle, telling him to use it upon the winged Ethereal Pegasus, who could withstand the mighty flames of Gehenna.  Bellerophon journeyed to the never-failing well Pirene, on  the citadel of Corinth, the one place where Pegasus drank from.  Once the bridle was set, the divine creature was as tame as a broken gelding.  Using the winged beast Bellerophon flew to Gehenna's home.  
Seeing the Great Chimera in person taught the boy into a fear he had never known before.  Just by beholding her he could tell that this was not a mere beast.  This was something that was not of this world.  However, Pegasus would not allow the young man to flee the scene, as it knew that it would result in it's master's death.  So the boy and his guardian flew into battle against Gehenna.  The Mother of Chimeras was bewildered at first at the pair attempting to attack her.  No mortal had dared strike her before.  But eventually she realized what the boy intended and fought back, spewing forth jets of flame that could melt granite.  Unbeknownst to her and the boy, the golden bridle that Pegasus bore, as well as the Ethereal itself were immune to all amounts of heat and fire.  Thus, the pair could not be harmed by her.  A might battle proceeded, which changed the landscape of the mountain forever.  Neither side seemed able to inflict harm upon the other, as Bellerophon's weapons were useless against Gehenna's hide, while Pegasus was far too swift for her claws, tail, and teeth.  
Until the young man was struck by an idea of how he might achieve victory.
Bellerophon attached a large block of lead to one of his spears.  He then had Pegasus fly head on at the Mother Of Chimeras, holding the spear out as far as he possibly could.  Gehenna had locked eyes upon this charge and drew forth an especially great breath, jaws gaping wide.  At the last second, the boy launched forth the block of lead into her mouth.  The Daughter of Echidna breathed forth, and the lead was melted by her exhalation.  Her throat blocked by the molten lead, the Mother of Chimeras could not breath.  Gehenna's death did not come easily or suddenly.  It was a half hour of struggling to breath, clawing at the earth and writhing in pain before she finally died.  The boy Bellerophon watched her death throes, horrified by her agony.  Once she was dead, he went forth to the body of the Great Chimera and wept over the cruel manner in which he killed her.  The event shaped the rest of his life, and the boy who one day became known as a hero for this deed never raised a weapon against any of her children for as long as he lived.

But Gehenna was not a beast which could be killed.
She was an ancient being, something to which the concept of 'death' could not and should not be applied.  A Paradox was formed around her and the boy Bellerophon.  The Olympians watched from a far, concerned.  The error needed to be corrected before it damaged the fabric of space and time.  Therefore, Hades had her body moved to the Underworld, placing her within Tartarus, the only place known of that could possibly hold such a being.  For all that was tossed within Angra Mainyu would never escape its grasp.  Within her living corpse, the consciousness of Gehenna was bewildered by these events.  What was happening?  Why had the boy killed her?  She had never harmed a human in her life before.  What were these beings?  Why was she being put in this dark place?  She could not understand what was going on.  At least, not at first.  Realization slowly dawned upon her as the energy beings slowly repaired the events surrounding her death.  
She had been imprisoned.  After being murdered.
She still did not understand why.  She had done nothing wrong.  
In truth, Gehenna was an animal.  A perfectly innocent creature that was the victim of petty human affairs.  

The ebony ichor within taught her.
Gehenna was a great creature, and so it took a long time for the liquid corruption to seep in.  But once it did, she was changed forever.  Angra Mainyu taught her injustice.  She had done nothing wrong, and had been killed for it.  Inevitably, she grew to hate the boy that slew her.  But not just the boy.  The man who sent him.  The beings who imprisoned her.  The black liquid within Tartarus seeped into her mighty corpse until she had grown to hate all beings but her own children.  They would all die for murdering her.  

For Angra Mainyu corrupts all things which it touches.

And so she would have remained within the depths of Tartarus, drowning in corruption and howling her ineffectual fury at existence and her prison.  How many years passed cannot be known.  How long was she submerged within the depths of Tartarus?  None know.

Until that day.
It was a small thing that he did.  Sitting upon his metallic throne, the Ragnarok Archon smiled.  This was not as something as simple as a grin.  This was an expression of victorious sadism.  A jeer nearly unmatched in its hatred and disdain of all things.  It could be felt, even from within the security of the Underworld, even within Tartarus.  Angra Mainyu held within could feel that grin and the intent of the one that wore it.  The ichor stilled.  
And it released its captive.  
As the wards surrounding Tartarus were meant only to hold Angra Mainyu within, Gehenna was able to escape with a modicum of effort.  Millions of lives were extinguished trying to stop her as she tore through the Underworld in a fury the likes of which the metropolis had never seen.  The Black King of the Realms Below grimly surveyed the carnage before him before reluctantly expelling her from the pocket dimension, into the world of Eternity's End.