The magic that conceals the true appearance of drow aboard Jarlaxle's ships doesn't extend to the Scarlet Marpenoth . Characters who encounter drow while sneaking around the submarine are questioned. If the drow don't get the answers they want, they attack. Any nearby drow who hear a fight break out will investigate and team up to repel boarders.
The Scarlet Marpenoth has AC 20, 300 hit points, a damage threshold of 15, and immunity to poison and psychic damage. The submarine's structural integrity fails when the vessel drops to 0 hit points, whereupon it floods and sinks.
The submarine has the following general features:
- Interior spaces are unlit. (The drow rely on darkvision to see.)
- All furnishings and features are bolted down.
- Chambers are 8 feet high, with 6-foot-high passages and doorways connecting them.
- Air magically circulates through a complex ventilation system and small metal grills set into the floors.
- Doors are made of steel and have AC 19, 27 hit points, a damage threshold of 10, and immunity to poison and psychic damage. A door's lock can be picked by a character who makes a successful DC 18 Dexterity check using thieves' tools. A door can be forced open by a character who succeeds on a DC 25 Strength (Athletics) check. Jarlaxle has keys to all locked doors. All doors are airtight while closed.