Seadeeps

Seadeeps was the sixth main level, and seventeenth level overall, of the Waterdhavian dungeon complex of Undermountain. By 1492 DR, it was the site of a brewing conflict between a mind flayer colony and a githyanki strike force.

Entrance
A tunnel descending from the Crystal Labyrinth led to a series of irregular branching caverns.

Exits
Several locations exited from Seadeeps:
 * A tunnel that descended to Vanrakdoom was heavily guarded by duergar who had been enslaved by the mind flayers.
 * A portal led to the Obstacle Course. It was heavily guarded by a githyanki patrol.
 * Another portal, located in an empty cavern, led to the Caverns of Ooze.
 * A third portal, located next to the device that powered the illithids' structures, led to Arcturiadoom.

History
Seadeeps was originally the site of two of Clan Melairkyn's main mining efforts. Its caverns were excavated by following the veins of mithral that extended westward under the floor of the Sea of Swords.

In the late 15 century DR, an illithid colony was established in Seadeeps, led by a ulitharid called Extremiton. The group had fled its main colony after a githyanki attack on the main colony deep in the Underdark, following the instructions of its elder brain. Despite the relative security provided by the dungeon, the colony was under threat of extermination by the githyanki group living in the Crystal Labyrinth.

Inhabitants
Extremiton and its mind flayer colony had plans to conquer Waterdeep. However, the city's vast population had made the ulitharid extremely curious. In order to better understand them, it built a series of psipods in the level, devices that could imprison sentient creatures in a dream version of Waterdeep called Alterdeep, crafted from information gathered telepathically from Waterdhavians' minds. The ulitharid then manifested itself in the illusion as any character it wished, although it showed a preference to appear as Durnan.

At the same time, a githyanki strike force, commanded by the knight Yaveklar, slowly opposed the mind flayers while awaiting reinforcements from the Crystal Labyrinth to conduct a final assault. In order to oppose the githyanki, the mind flayers bred a neothelid, which they planned to unleash upon them on both levels.

Additionally, a cloister of flumphs inhabited a tall cavern on the outskirts of the level, feeding off the mind flayers' and githyanki's psionic energy from a safe distance. The githyanki slaughtered any flumphs they encountered on sight.

Appearances

 * Adventures
 * Expedition to Undermountain • Halls of Undermountain • Waterdeep: Dungeon of the Mad Mage
 * The Ruins of Undermountain
 * The Ruins of Undermountain