Into the Depths

===Into the Depths of... an island?===
This is an expansion of the campaign narrative in Lord Beresford's Travellers in Tibet.
A Diversion amongst the Greek Isles
The party's travel plans went awry almost immediately: sailing through the Greek islands, their ship ground to a halt under the magical influence of a Remora, and a raiding-party of Fishmen climbed aboard. In a hard-fought and closely-matched battle which left two of the party near-death from their wounds, newest PC Stanley was grappled and dragged overboard but managed to fight his way back to the surface. Three crewmen were not so lucky, and were carried off into the deep by the Fishmen.
After the battle,a Merman surfaced and called for help. His home village was also attacked by this same band of Fishmen, and prisoners taken. He told the party that the crewmen would still be alive, and his story is borne out by the fact that each of the raiders carried a magic stone which allow air-breathers to breathe underwater – they found two on the bodies of the Fishmen they killed. 
The Merman can guide them to where the prisoners are being taken: a grotto under a nearby island.
He had already scouted it and saw that it led to a dry cave, where he and the posse his relatives are currenly assembling would be helpless. (They have fish-tails, the Fishmen are bipedal.) He appeals for them to help. 
The party saw that the grotto was a big obstacle: speargun (well, spear-crossbow) armed Fishmen underwater, two sharks in a cage off to one side, and who knew what was awaiting them above the surface.
First they explored the island, finding a big bubble of translucent rock-like material of massive density and hardness. Bemoaning their lack of dynamite (“I'm never getting on a train without dynamite again.”) they decided that they couldn't break through it. (So wedded are they to their 'modern' tech, they never even asked if the locals could gather together a decent amount of black powder that might do the job!) Local children confirmed that there were cavities in the rock which smell of the sea, or through which they sometimes heard the 'voice of spirits' – but none of them are wide enough to get all the way down. So the party decided they had to pass through that grotto killing-ground.
Scouting found that the side-cave holding the sharks behind bars was a through-channel, necessary so that the water they were being held in didn't get too stagnant and suffocate them. There were bars at the back of the cage too, but the crucial difference was that these couldn't be seen by the guards. Two PCs dived down and sawed through the bottom of the back bars, attached ropes, and swam out to the surface, from which they pulled the ropes and bent the bars to release the sharks, luring them out by dripping fish-guts into the water.
With the aid of the Merman making a diversion at the grotto entrance, the PCs managed to get to the shark-gate and open it before the Fishmen noticed them, restricting the fishmen's advantage with the spearbows and getting in close for a melee. 
A tight fight ensued, firstly with the two underwater sentries, then up into the dry cave where they found four blunderbuss-armed fishmen. Once again the party only just survived, three of them taking crippling injuries (none of which, fortunately, were permanent). But Siena healed them all up and they pressed on.
The great cavern under the 'bubble' turned out to be a artificial sphere, one-third filled with sea-water, in which the Fishmen had a village which they had thought to be safe from all their enemies. Landsmen couldn't get through the grotto, mermen, sharks and the like couldn't pass through the dry cave. The arrival of the PCs was a shock, especially as only the Fishwives and their children were present. All the Fishmen were out raiding.
The PCs did not devastate the village, though, but just passed through it into a long pitch-black corridor. They took the hurricane lanterns which had illuminated the landing-cave to light their way. This made them perfect targets for the two Fishmen waiting in their dark guard-station. Sudden well-aimed shots from the darkness inflicted yet more damage before the party managed to throw a lantern forwards to illuminate them and blast them with more modern weaponry.
That gave them a warning – it's not a good idea to advance into a dark tunnel carrying the only light-sources around when the opposition have guns! They did their best to shade the lanterns so that their light only went forwards, not illuminating the people around the lanterns.
And when they saw the tunnel opening out ahead, they stopped and Victoria sneaked forward in complete darkness to look at what was in store for them. 
Another sphere, this time only half the size of the 'village', but still a hundred yards across. About a third was filled with water, in the middle of which stood a finely preserved Ancient Greek temple, whose eternal-flame door-pillars provided the only light in the vast space. Two lines of bouys were just about visible in the dark water, and a rough wooden walkway which spiralled around the edge of the sphere to run from the tunnel exit to the water's edge.
As a glimmer of light escaped the tunnel edge, a voice cried out in Greek – fortunately, our heroes' public-school education included the classics so they understood “It's an ambush!” before the cry of pain which ended that prisoner's attempt to be helpful.
Not knowing how well the Fishmen could see in the dark, the PCs guessed that, adapted to the depths of the sea, their low-light vision would be far superior to that of humans. Going into the sphere without lights would be suicide. They returned to the now-deserted village (the Fishwives were taking no chances that they would be as lenient on their way out!), they dismantled a couple of the huts to make themselves pavises, and hung the captured lanterns on the outside to throw some light outwards without (they hoped) making themselves too visible behind the great shields.
They crept along the spiralling walkway. Three of the party carried the great shields, the others had rifles in hand, ready to shoot at anything they saw. Most of the shots came from behind them, well-aimed through the gaps between the brightly-lit shields, the PCs only able to snap-shoot back at the muzzleflashes in the darkness. They shifted the shields to give them better covering from behind, only to take fire from closer range ahead, on the walkway. But that gave them a better chance of hitting with their return shots, and it wasn't long before a cry of pain told that they had been successful.
Reaching the end of the walkway, they found that it ended at the edge of the water – there was no bridge. They moved around the edge instead, heading for the bouys in case that marked a way across. But as they went across they were once again attacked – this time at very short range. The fishman they had wounded on the walkway, and his partner, had only retreated under it and were therefore shooting at point-blank range from the darkness into the figures silhoutted against the lights of the temple. A brief and brutal exhange of fire splattered both fishmen against the rock, but left another crippled party member.
The line of bouys did not mark a walkway or stepping-stones. Fearful that they might confine a deadly predator – and they didn't know which side of the bouys it would be – the party decided to throw something in the water to check. Once again Victoria volunteered, and scuttled out into the darkness to drag a dead Fishman back. Her guess was right – even though she was clear of the protective shields, the fishmen couldn't see her in absolute darkness.
Throwing fishman limbs into the water had a surprising result. The water roiled, as expected, but then a merman appeared. Two fishmen had been holding the merfolk down below with crossbows, and their disgust at seeing their comrade's dismembered parts had been distraction enough – the mermen managed to catch them off-guard for an instant and beat them, 
Now they had allies in the water.
The party supplied the mermen with all the fishmen crossbows they had captured and converted the grenades they had jury-rigged from the fishmen's black powder charges for the blunderbusses into bright Roman Candle-style fireworks. These lit the spherical cavern enough for the combination of PCs with hunting rifles and mermen at the shores of the water to take on the remaining Fishmen around the cavern.
That left four of them, and the human prisoners, inside the temple on the lake. Two of the party crept away and set up a distraction. Pistols lashed to legs of the walkway with string round their triggers allowed them to start shooting again at a distance, in the hope of luring the mermen inside to shoot at the muzzle-flashes, or at least keeping their attention away from where the merfolk were swiftly towing the other four PCs to the far side of the temple. It seemed to be working – the fishmen inside the temple were soon shooting out, giving the snipers a chance to shoot back at the muzzleflashes, and a good-sized skirmish seemed to be going on.
Two of the party's swimmers climbed up the wall of the temple to a window. The others took the more conventional approach and landed on the porch to enter through the doors. The climbers caught the outlines of a fishman just inside the door, light glittering on his ready spear. They called out a warning of the ambush, then realised they had attracted attention to themselves. They were silhoutted in the window while the fishmen were in complete darkness below, so they jumped through the window.
The two fishmen in ambush abandoned it and charged them, giving the heroes a hard time in the first couple of seconds. The other party members rushed through the door to the rescue, only to take close-range shots as they were momentarily outlined against the flames outside – two fishmen in the complex still had loaded blunderbusses. 
Then it was the same as it had been below the water. The human prisoners were being held at gunpoint, but with both guns simultaneously unloaded, they rushed the fishmen and swarmed over them.
The climbing PCs meanwhile managed to beat their opponents, only noticing later that the fishmen had both been fighting one-handed with two-handed spears, each of them having taken a wound which crippled their weapon arm or hand in the preceding gunfight.
I found this a great way of evening the odds and presenting the players with a tactical challenge. If you would like some hints on running something similar, read The Fishmen in the Sphere.
Category:Adventures