This is a summation of episode 6 of the Landscape season 3.
The adventurers dive deeper into the trench, piloting their newly acquired Sahuagin submersibles. Following the notations on a set of sea charts found in one of the subs, they make their way to and past several Sahuagin villages, made out of a varied set of much larger submersibles similar to the ones the group has stolen. Each village is attending to various types of activities, some stripping down plundered merchant ships, some exclusively tending to massive shark shoals.
At what appears to be the largest of the camps, where aquatic elves have been enslaved to manufacture more submersibles, Zanos spots a set of massive octopus tentacles camouflaged and lying amongst the buildings. Solomon and Saallizaar free two of the elves and question them. It seems that the Sahuagin have taken to worshipping the giant octopus, and the elves claim it is both intelligent and malevolent.
Tophat and Solomon decide to investigate, and sneak their way up to the octopus and reveal themselves. Tophat announces himself as the Emissary of Death with a message for the creature, and the invertebrate welcomes him and Solomon by swallowing them whole.
Within the creature's stomach, Tophat and Solomon meet three mindflayers, who have been controlling the octopus and forcing the Sahuagin to conduct raids in order to find precious artefacts lost to the Underdark in a flood many years ago. Tophat uses this information to his advantage and convinces the Illithid trio that a huge convoy of merchant ships would be arriving at Esakar Landing in 6 weeks, and he needs every soul on board those ships to die to harvest their souls for Death. The mindflayers agree to do so, but not without some suspicions.
The group hastens back to Esakar Landing to make preparations, including sending word to Karthoogh of an imminent pirate attack, and placing decoy ships to feint the Sahuagin into committing their full forces.