The Stygian Sea

January 14th, 2023

This is a rules supplement for running a flooded Avernus in Dungeons & Dragons 5th Edition, including rules for creating infernal ships, examples of some of the vehicles and creatures a party might encounter on the Stygian Sea, and some aquatic charms a fiend can offer in this modified setting.



This content was written to be compatible with Dungeons & Dragons 5th Edition. It makes the following modifications from the Systems Reference Document:

  • “Species” is used in place of “race” and “ancestry” or “variant” in place of “subrace”.
  • This document uses new traits called Condition Resistance and Condition Vulnerability. Resistance to a condition means that a creature has Advantage on Saving Throws made to resist that condition, and vulnerability to a condition means that a creature has Disadvantage on such Saving Throws.
  • Damage and condition resistance, vulnerability, and immunity are now grouped together as ResistancesVulnerabilities, and Immunities respectively.
  • Resistance, vulnerability, and immunity to Poison apply to both the damage type and the Poisoned condition.


The Stygian Sea is © 2020 Mario Panighetti. Licensed under CC BY-NC-SA 4.0.

Certain materials are included under fair use exemption of the U.S. Copyright Law and are restricted from further use. These materials, including references to game mechanics, are not approved or endorsed by Wizards of the Coast and do not constitute any license or agreement with Wizards of the Coast.

Third-Party Content References

Dungeon Master’s Guide © 2014 Wizards of the Coast LLC.

Systems Reference Document 5.1 (“SRD 5.1”) © 2016 Wizards of the Coast LLC. Licensed under CC BY 4.0.

Baldur’s Gate: Descent into Avernus © 2019 Wizards of the Coast LLC.

Mordenkainen Presents: Monsters of the Multiverse © 2022 Wizards of the Coast LLC.