Yes, this references Supernatural.
There are five rivers of the Underworld. Lethe and Styx and Cocytus and Acheron and Phlegethon. They differ in their effect upon their victims, but their essence is the same. They are the rivers of the realm of the dead, its moats and its ducking ponds. They ensure the security of Hades' realm and the suffering of his serfs.
Phlegethon is the sustainer. It is the artery of Tartarus, the energy of Hades, all of its measly vitality. It flows under the gardens of Persephone and her husband's palace, fuels the sun in Elysium, and runs through the fields of pain and suffering as it chains the tormented to eternal wakefulness.
Its counterpart is Cocytus, the sluggish vein to its red-golden arterial rapids. Sorrow leads to despair which then leads to the sleep of death—or is it the sleep of the dead? Either way, few pass it without losing their will to live. They drown in despair, and do not escape, collapse catatonic upon its icy banks. Cocytus is a moat.
Born of Cocytus is the Acheron, suffering, pain, and most crushing of all, guilt. It is one of the two rivers which water Nyx's Nightmares, the other being Phlegethon. To stand by the streamside would break a lesser man, or even a greater one, for is it not the greatest who shoulder the heaviest burdens and suffer the greatest losses? No untrained mind survives a submersion into its unfathomable depths, and it is tempting, so very tempting, to give in, to slip into its waters—you deserve no better, after all. Acheron breaks the righteous and the good. It shatters and shapes the steel-spined into self-recriminating wrecks.
Then there is the Styx. It is the border between life and death, liquid, all-consuming hatred. It burns cold until it is cold enough to burn, it is acid, corrosive, clogged with broken dreams and traversed only by Charon's ferry. The Styx is the ultimate and outermost moat of the land of the dead, the first and last defense. You notice that there have only been four rivers written here. The fifth is Lethe. Oblivion. Non-being and the void. A concept beyond mortal comprehension. Of Hades' rivers, it flows apart, never converging into the witchfire-filled marsh with the other four. The rivers above were introduced in the order of usage. When a soul rebels, it is first tortured with fire, and when fire does not destroy it, despair will neutralize it. Like a song,
If that despair doesn't work,
Then guilt's river will make you hurt;
And if guilt is truly not enough,
The Styx will certainly be up to snuff.
Sung to the tune of "Mama'll buy you a mocking bird", this refers to the escalating series of procedures a dangerous soul will be subjected to. If none of the above methods work, then the final solution is complete erasure from existence. Lethe is a permanent solution to troublesome souls, and its potency only increases with prolonged exposure. Certain spirits and divinities may have some degree of immunity, but the closer they go to the origin of this river that, according to Dante, flows from the steps of God's throne, and which, according to the lore of Night's Queen, eldest and endless, originates from the entity who was the end, as Yahweh was the beginning, Amara. Lethe is the end of all things. For without memory, without experience, without life, there is no identity. A blank slate, wiped clean. No skill, no talent, no desire. All that ever made an individual now gone, leaving a Tabula Rasa in its place.
That is the answer for "dispositions". Imperfect erasure results in bleed-through from previous lives. That, combined with the uniqueness of each shell of flesh, combine to create a new person.
Among those god-touched children of two worlds, there is a prince of the Underworld. Access to its resources is easy. The dead's suffering becomes the succor of the living.
Reviews, prompts, and advice are always appreciated!
