The Tartyx river forms the boundary between the mortal realm of the Theros and the Underworld. It is also known as the "Rivers that Ring the World" as it is formed from the confluence of five tributaries, each originating in one of the five wards of the Underworld.
Although the Underworld is dark, it is ironically not connected to Nyx, as it lacks the night as much as it lacks the Sun. Its landscape is characterized by huge columns, and giant chains and poplar trees.
The Underworld is governed by the god Erebos, cast into the place by a frightened and paranoid Heliod after his birth. Erebos rules the Underworld with an iron whip. Jealous, tyrannical and paranoid, he creates monsters to guard his realm. Skeleton soldiers called phylaskia guard the borders, and so does Kunoros, Hound of Athreos. Some souls in the Underworld become twisted and hateful over the course of their afterlife. The most evil and malicious of them also transform into horrible monsters. Many other souls find their memories and identity gradually eroding away, until they become lifeless statues known as misera.
Thousands of years ago, the gods waged war against the titans, their predecessors. Victorious, the gods sealed the titans in the Underworld. If they would ever be freed, they would inflict unspeakable horrors on Theros.
After the fall of the Archon empires of the Age of Trax, some of the archons took refuge in the Underworld. There, their minds, souls and bodies were twisted, turning them into sadistic monsters known as the Ashen Riders.
Different sections of the Underworld are aligned with the five colors of mana.
- Agonas, in whose arenas honorless fighters are doomed to fight forever. It is aligned with red mana.
- Phylias, a tedious place for ordinary or indifferent souls whose lives were uninspired. It is aligned with white mana.
- The glassy oceans of Nerono, are the final resting place for souls haunted by their memories and drowned sailors. It is aligned with blue mana.
- The Labyrinth of Memories is a maze of waterways in the Underworld that traps travelers by sending them in circles for eternity. Sirens torment lost souls by whispering true directions -- words that fade immediately from the listener's mind.
- Ilysia, a protected realm as tranquil and vibrant as the rest of the Underworld is bleak. Those who die as heroes are permitted to dwell here. It is aligned with green mana.
- The bleak realm of Tizerus, outside the palace of Erebos, where all hope crumbles to dust. This is the final punishment of murderers and those who have committed unforgivable offenses against the gods themselves. Demons, Underworld harpies, lamias and nightmares compete for the chance to haul the doomed away to their own personal torture. It is aligned with black mana.
- The Mire of Punishment: where those caught attempting to escape the Underworld spend the rest of their existence.
- Associated cards:
- Depicted in:
- Referred to:
- Wizards RPG Team (2020), D&D Mythic Odysseys of Theros, Wizards of the Coast
- Donny Caltrider (January 23, 2020). "Sam Burley Talks About His Theros Beyond Death Lands". Hipsters of the Coast.
- The Magic Creative Team (August 21, 2013). "Planeswalker's Guide to Theros". magicthegathering.com. Wizards of the Coast.
- Erebos, Bleak-Hearted. Reddit (December 30, 2019).
- Flavor text for Underworld Sentinel
- Woe Strider. Reddit (December 30, 2019).
- Flavor text for Final Death
- The Vorthos Cast (February 10, 2020). "This week we have special guest James Wyatt from Wizards of the Coast on to talk about Theros: Beyond Death.". The Vorthos Cast.
- Flavor text for Final Flare
- Flavor text for Dreadful Apathy
- Flavor text for Memory Drain
- Flavor text for Ilysian Caryatid
- Flavor text for Fruit of Tizerus and Cling to Dust
- Flavor text for Mire's Grasp