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The Scarlet Marpenoth was a submarine secretly owned by Jarlaxle Baenre.[1] It was named for the month of Marpenoth.


The Scarlet Marpenoth was a red vehicle shaped like a manta ray.[2]

The submarine had a top speed of 2 mph (3.2 km/h) and required a minimum crew of two in order to be properly piloted and kept. Its interior was always kept dark, so that its crew had to rely on darkvision. The ship was maintained by a crew of rock gnome engineers and run by a drow crew under Jarlaxle's command.[1]

The ship's air supply circulated between all its chambers through a complex ventilation system powered by quasi-magical machinery. Its airtight doors were kept always locked.[1]

The Scarlet Marpenoth's engine was a quasi-magical device that controlled the ship's depth, as well as the steering fins and rudder, and powered its propulsion system. It could be piloted from the ship's control room.[1]

The ship had a defense system that allowed its outer hull to become electrified for a short period of time.[1]


According to a commemorative plaque in the House of Inspired Hands, the submersible was launched in 1489 DR.[2] The ship was designed and built in the island-nation of Lantan.[3]

In 1491 DR, one year before the arrival of the Sea Maidens Faire in Waterdeep, the submarine was acquired by Jarlaxle and was kept secret even to the crews of the Faire's sailing ships.[3][note 1]



The Scarlet Marpenoth is obviously named after the submarine from The Hunt for Red October, with Marpenoth and October both being the tenth month of their calendars. Probably unrelated, there is the Year of Crimson Marpenoth, −411 DR, as envisioned by Augathra the Mad.


  1. Canon material does not provide a year for the events described in Waterdeep: Dragon Heist, but Christopher Perkins answered a question via Twitter and stated the year was 1492 DR. Corroborating this, Dragon Heist page 20 refers to events of Death Masks (set in 1491 DR) as being "last year". Unless a canon source contradicts this assertion, this wiki will use 1492 DR for events related to this sourcebook and Waterdeep: Dungeon of the Mad Mage (which is referenced on pages 5 and 98 of Dragon Heist).