The group splits up to begin searching the ship. Doral checks over the bodies on the upper deck and finds at least three pirates still alive. Glaive sets about securing them with ropes and moving them back to the longboat. Midian finds an elevated position to look around the ship. The waters around it are now teeming with reef sharks drawn by the scent of blood in the water. The bulk of the giant crab is still visible off the starboard side. Doral searches the upper deck and sets aside a number of weapons, rings, trinkets, and other valuables from the bodies of the crewmen. He heads below with Kraken to make sure there are no more surprises waiting below. Being familiar with the basic layout of ships, Kraken leads the way to the captains quarters. The door to it and a side room for guests stand open. Searching both rooms reveals numerous documents, charts, maps, and ledgers no doubt containing plenty of useful information. Everything is quickly snapped up along with the footlockers from both rooms. Nearby is a heavily chained door made of stout wood. Krakens sword is ill suited to chopping through the thick material but a quick search of the captains body comes up with a heavy iron key that fits the lock. There are several clicks when the key is turned as various spring loaded traps have their safeties set. Once inside the room you can see why it was so heavily protected. Three darkwood chests sit chained to the floor. Prying open the first one reveals a massive collection of gold jewelry, gems, and goblets. The second chest is piled high with coins. The last chest contains the finest silks and delicate looking statues.
Working quickly, the group moves the chests, looted goods, and the three unconscious pirates to the longboat. A search of the lower levels is attempted but the rapidly rising water causes issues. Recognizing the danger, Kraken urges you all to leave immediately before you're pulled under along with the ship. Shortly after you depart, the ship settles on the bottom of the harbor more or less upright. Only its masts protrude from the water.
The return to your own ship is uneventful though Midian had to drive off some of the larger sharks that approached your boat. The crew cheers at your return and eagerly press you for word on the attack. The three pirates are taken below and chained up to await your questioning. Your chests are moved to your rooms for now, though the captain offers use of his armory for storing the weapons as only himself, the first officer, and the quartermaster has access to it. You take some time to relax, have a meal, and tend to your wounds before going to revive the prisoners. They spit at you, call you cowards, and demand you face them one on one. All three of them are heavily muscled, scarred, and tattooed. You try to talk them into giving you what you want as peacefully as you can, but it takes a few cuffs to the side of the head and threats of keelhauling them before they start to talk. They tell you that a group of captains had been hired by a group calling themselves the Servents of Flame and Shadow. The work had been easy, mostly ferrying supplies to the island, building the docks, hauling gear inland, and sinking any ships that tried to make landfall nearby. The cultists worked with the undead. They used them heavily for guarding the work parties and supply trains. The pirates knew that they were taking slaves to some mine but that is the extent of their knowledge of their activities. A day ago the survivors of your attack reached the ship and they were preparing to leave the island when you attacked again. The only cultist who survived was Ucarin, the one who controlled the Horror of the Black Depths. His master was Kresh, a singularly evil man who had removed his own face to graft the skull of a fearsome beast. All of the pirates feared him due to his tendancy to kill any of the lower ranked men who angered him and reanimating them for his use.
The documents you took tell you more about their operations but leave a lot of questions unanswered. The captain kept a detailed log of where the ship went, sightings of other ships, attacks, damage taken, and supplies used. From what you can tell they would regularly make trips to other populated islands to pick up supplies. Sometimes these were goods and sometimes they were slaves. You can't determine a base of operations from these details, it looks like the cultists used agents in multiple cities to get what they needed. There is only a little information in Ucarin's cabin, only a single letter written by Kresh to him. It details why the mine site was so important to them. According to him, the island was once a terrible battlefield long ago. Dragons fought demons against the backdrop of an active volcano. One of the mightiest dragons fought an army of demons on the slopes there. When the volcano erupted it covered dragons and demons alike, burying them beneath tons of ash and stone. Many of the demons became trapped, but still alive in a sense. Unable to move their bodies, they sent their essence questing outwards to find an escape or creature to possess. Nearly all of them were drawn to the Khyber shards like metal filings are drawn to the magnet. Once there their essence was trapped and the bodies died. The crystals don't show any outward signs of contamination of demonic spirits. However when a crafter attempted to bind a spirit to the shard they discovered that something was already present in the crystals. A skilled artificer can construct a means of tapping into the demons power to use it for their own end. However if the shard is damaged the essence is released and can attempt to possess a new host. Kresh spoke of massive crystal deposits that contain the entombed essences of "demonic generals whose powers are like that of a god". His plan was to use those essences to reanimate the body of the great dragon. It would be an abomination to the scaley kind. With the strength of the great wyrm, the benefits and immunities of undeath, and all the powers of a demon lord it would be unstoppable. Nearly so, as it turned out. You cannot imagine the kind of destruction it might have caused if it hadn't still been mostly entombed in the stone.
The rest of the trip back to Cliffscrape is calm. The wind remains fair and you are able to make good time. Upon your return Creidan, the House Tharask local manager, meets you at the docks to greet you and invite you back to hear your tales. Johan and Seria bid you farewell, having decided to go their seperate ways. Johan heads north, chasing rumors of an order of paladins bringing relief to some villages that had been raided. Seria catches a caravan headed for the city of Sharn, via the long road.