The only temple of Myrkul that was established after the Time of Troubles during the 14th century DR. The temple was magically constructed by three Myrkulyte cleric-liches on the seabed under the Sea of Swords where they continued to venerate the Lord of Bones beyond his destruction on Toril.
This location is sacred, as it was chosen due to the events atop the Blackstaff Tower in Waterdeep in 1358 DR. When Myrkul's avatar was on the verge of exploding with grim energy, dimension door was cast in effort to transport his body away from the city, spewing forth a mephitic cloud of death that rained down in a 5 mile radius.
The sea floor in this area continuously produces throngs of aquatic undead, including lacedons and undersea zombies. The temple was erected in the center. The temple is protected by a number of monstrous sea creatures, including an undead kraken and horribly mutated sahuagin.