13 A, 10 B, 1 C. Ok, military solution it is. Onwards.
Oh, before the update, a word. Voting an option 'because it's the most interesting' is legit, sure, but don't expect it to go well, generally. I think it's a good chunk of the reasons the Obsidian Embers arc ended up as it did. Just a warning. Choose, but choose thinking about it. Not just because it's cool.
The young king stood up in the council chamber, raising his hands in an appeasing gesture: "Heed my words, my prized and wise advisors. After hearing your opinions, I have come to a decision. We will undertake a grand military expedition, to rid our caves of the monstrous threat besieging them....."
(Taken from 'Life and Deeds of King Saras the First')
The king slammed his palm on the table again: "Just shut up, all of you! I can't hear myself thinking, damn it! - he sat again, smirking – the general has a point. We can't just sit here, hoping for the best – he glanced meaningfully at the high priest – those monsters aren't just going to 'go away'. Yet, the Sealed Corridors must be sealed for a reason. I'm not going to go against our only historic and sacred texts just because someone thinks it's a good idea. It's not."
He continued: "Now, general, you will receive your orders. You are to select five hundred of your best men. I will take command of the expedition myself. I want to find out what happened to my father Restil. Don't think I haven't heard the reports of screams in the tunnels the day he and his party left."
The council, suddenly in agreement, started protesting that the king could not risk his life in a fool's errand. The general and his second both volunteered, with the high priest trying to convince the youth to stay in the capital.
The king growled and slammed his palm for a third time on the table: "Enough! I gave you your orders, just go!"
The advisors bowed and filed out of the room, still whispering.
In the following days, the expedition was prepared. Five hundreds soldiers, armed and armored with the best forge-iron, gathered at the entrance of the eastern cave system. A single tunnel headed away from the fortifications.
Long pole-lanterns, containing glowing lichens, were given to the men in the front. The expedition carried with them a slab of stone covered with the map of the small part of the cave system that had been explored by scouts during the long years.
The tunnel headed east for close to a kilometre, then opened in a large cave, almost fifty meters long and just as wide. From there, several tunnels left, heading in all directions, that forked again and again, sometimes criss-crossing, sometimes ending abruptly.
Beyond that, nobody knew what to expect. The only sure thing was the labyrinthine nature of the cave system.
The men left in good order, pole-lanterns at the front, heavily armored men carrying great shields and axes just past them. Attacks were expected even before reaching the cavern.
Less than an hour of marching saw the small army reach the cave. And find out the answer the young king was seeking.
King Restil had left the main cave with close to an hundred men. Those who still were vigorous enough armed, fifty of them. The rest just carrying their clothes and some supplies. The scene that presented itself to the army was gruesome. Corpses lay everywhere, the stench of blood was overwhelming. Most of the corpses still wore their armor. Yet many were literally ripped open, pieces of their bodies scattered around the cave. A leg here, an arm there, an headless torso over there.
King Saras moved aside his bodyguard and came to the forefront, surveying the scenario with a frown. He ordered sentries to be posted at all cave entrances, with most of the main army gathered in the middle to respond to any threat. He and twenty men would search through the scattered corpses.
The young king immediately headed to his father's corpse, easily identified by the decorations on his armor. He had been torn to shreds, his head a ruin. The king knelt in front of the body, closing his eyes and murmuring 'Father.... why?'. He stayed still for a long time, then steeled himself and stood up. He turned to his retinue: "Start gathering the bodies. They deserve to be cremated with all honors. What they did was for our survival."
The bloody task lasted a few hours. The bodies were carried back to the main cave, where a great funereal pyre would be prepared in the next days.
Once the task was completed, the king gathered his officers, asking: "What did you notice? I saw three things of interest."
A young officer was the first to speak: "My king. There is not a single beast corpse. Several of the men that accompanied your honored father were veterans. It is unconceivable they were slaughtered to the last man without exacting a bloody toll. I think the beasts carried their dead away. To what purpose, I do not know."
The king nodded: "Very well. Anything more?"
Another officers spoke up: "There aren't enough bodies. Half of the expedition was made of miners, fishers and gatherers. They left unarmored and often unarmed. I can't see any unarmored body here. Although it is too horrible to contemplate, I think they were taken away. Alive or dead, I do not know."
The king nodded again: "Yes, exactly, that's the second thing. Anything else?"
A few seconds passed, then the king sighed: "Look at the weapons. All the weapons I can see on the ground are broken, probably during the fight. But there are not enough to account for the whole expedition. I think the beasts took them. Expect to face armed monstruosities during the expedition. We will need to plan this carefully. For now we will retreat to attend the cremation ceremony. I won't push blindly forwards in this labyrinth, knowing our foes are more intelligent than we first thought."
The army went back to the main cave. A great funereal pyre was prepared, with most of the nation attending. Tears were shed, but the main sentiment was fury against the beasts that had done the massacre.
The king gathered his military advisors to plan the coming campaign. The nation had at its disposal two thousand soldiers, all armed with close range weapons and heavily armored. The coming campaign would test the limits of the army...
Ok, this is going to be an open update, since there are too many variables. Write me up a plan on how you want to proceed with this. Keep in mind you're facing an enemy of unknown numbers, unknown location, hidden inside a veritable labyrinth. How many men will you send in? Scouting parties, a monolithic army? How will you explore the cave system? Will you build fortifications at key locations, once/if you find them? How many men will actually go on the offensive and how many will stay back manning the main fortifications/other fortifications?
Voting on. If you have questions ask away, I know this vote is somewhat vague. I'll answer to what I can (in case I forgot to mention something I'm taking as a given, since I know everything of what's going on)