Most of the plaques seem to be self-indulgent tripe, cultists gloating over their kills.

The last one seems to be different somehow, the one about a certain Ergun Nigma. On closer inspection, you find that the plaque pulls out from the wall by about an inch, and then can be rotated freely.

It is impossible to say for sure about the pit trap from down here, all of the important mechanisms are fifty feet overhead.  You will have to get up there in order to properly assess how difficult it will be to repair.

As Eya inspects the inscriptions and finds the mysterious plaque, her eyes widen a bit and she says, "Kiven, Respar, come check this out. It seems like something is strange about this plaque for Egon Nigma. I noticed that it can be pulled out a bit and seems to be able to rotate."

Kiven returns to the trophy room at Eya's call and scans the plague wall for magic.  He peers at the plaque Eya has pulled out and any space behind it, looking for a mechanism of some kind.

There's no visible mechanism behind the plaque, it simply attaches to a rod that passes into the stone.

   Abraxxus looks up at the hole above.  " I will check this out up there. " He flaps his wings and soars upwards towards the large hole.  The half-dragon will find somewhere to land and examine the room up above. 

Perception: 

20

Abraxxus finds himself in a kill hall very similar to the one at the start of the prior floor. Stairs at one end, a pikeman's post at the other, arrow slits to the sides, but this time a pit trap adds to the defense.

  He glides back down below and shares what he saw above.  " We need to build up our forces more.  Why don't we recruit some orcs and ogres to help defend it?" 

Eya makes note of the clicking and reads the inscription more carefully. After a moment to think, she says to the others, "Let's try something." She rotates the plaque three turns to the left, two to the right, then one last time to the left. 

Eya rotates the nameplate in the order that she'd derived from the nameplate's riddle, and there is a chunking noise as something shifts. A nearby stone in the wall pops out by a few inches, and now can be pulled away from the wall to reveal a small lead lined space within. Inside is a small sack of platinum coins, a fair sized ruby, a ring, and a set of manacles. The manacles glow with a faint enchantment aura.

Blau, up to this point following along silently, speaks up about the specter. "If she's been dead for so long, and she doesn't realize it, would there be any advantage to letting her loose in the caverns, to add to the defenses?" 

On the repair of the traps and various defenses, Blau adds "Every coin we find is going to be spent before we find it. Not even mentioning the laborers we will have to hire to do the small work. I shall pray to Lord Asmodeus for guidance in defending his goal, when we rest."

"Well done, Eya.  IoG?  That is likely to be Iris of Ghastenhall from the 6th inscription from the end."  Kiven examines the Iris of Ghastenhall inscription once more for any secrets.

Peering at the manacles Eya found, Kiven states "the enchantment would seem to subdue the captive further, quelling their desire to attempt an escape."

https://www.d20pfsrd.com/magic-items/wondrous-items/m-p/manacles-of-cooperation/

"Why would they save her ring in a secret chamber? Could it be the spectre who is this Iris being? Perhaps it provides some kind of control." Blau asks.

"These are all good questions Blau. We should definitely hold onto these items."

To Kiven, Eya replies, “Iris of Ghastenhall, dead from a broken heart and a poison dagger.” Hmm, perhaps this was their ring or the ring of someone important to them? We should try to fix up all these rooms and traps, but let's map out the rest of this place completely first," Eya suggests.

"How about we go north next?" she asks.

The group heads north, stepping into a small chamber. It looks like some kind of waiting room, eventually it becomes apparent that sacrifices would be held here until the ritual for them was complete. A broken door on the eastern wall leads outside, to a set of hidden stairs that wind upwards.

Moving north rather than up, you step into a large temple with an impressive vaulted ceiling. Six great stone columns support the room, and every surface is covered with baroque scenes of daemons and cultists marching together to war and slaughter.

A large throne sits on the eastern end, carved with images of demons slaughtering angels in creative ways. To Kiven's eyes, it radiates a moderate conjuration aura. Almost hidden among the imagery is a nonsense word written in abyssal script. "Yah"

The group quickly moves through the remaining rooms on this floor. Its mostly more of the same, broken bits of furniture giving some hints as to each room's former function, but this place is quite dead. A few interesting things are still found.

West of the temple is a magical fountain, featuring the shepherd of the dead, Charon, aboard his skiff. The skeletal figure constantly bleeds into the pool below, but the red liquid turns clear as soon as it hits the basin. To all appearances, in spite of the rather macabre source, the fountain is full of clear and clean water.

In one set of quarters you find a journal belonging to a lowly acolyte called Zander Trask. Its rather dull and poorly written, at first glance just a day to day record of his drudgery and rather uninsightful thoughts. There's enough here that it will take a few hours to read through for any interesting information that might be hidden there.

A guard's bed yields a small coin purse and a potion of some sort somehow missed in the ransacking of this place.

And then there is the tavern, a garish sign proclaims it to be the Death's Head tavern, it is apparently where the cultists enjoyed themselves in between whatever grisly fun their rituals called for. Its been looted like the rest of the place, but the damage here is relatively minor.

The last room you find on this floor is the Larder. To Kiven's eyes, the whole place shines with a mild Transmutation aura. Pinned to the wall with a large spear is a minotaur. The blood and body are fresh, this creature looks as if it died yesterday.

Spellcraft: throne:  22

Spellcraft: fountain:  25

Kiven collects Zander Trask's journal.  He shakes his head at it at first considering how dim witted Zander seems to be, but then decided even Zander could mention the location of the emeralds so he pockets the journal for some reading later.

Spellcraft: potion:  31

"Ah, how convenient.  The magic here will keep our food stores fresh indefinitely.  Just do not spend too much time in here yourself.  Such magical is... unnatural... when applied to humanoid flesh."

"Grumblejack, do you like fresh minotaur?  He's good as new!"

(Recorded 6 gold, 2 silver for Kiven.)

Eya looks around at the various oddities and turns to address the whole group, "You know, this place isn't so bad if we fix it up. Fresh water and food, as well as a bar. Perhaps this won't be so bad. Still, we need some help if we are going to operate a lair of this size. I'll send a message out for help tonight. For now, let's continue to the second floor."

 Kiven takes a moment to sit on the throne and thumb through Zander's journal some more.

He informs the group that the water is likely safe to drink, pending a check from Blau perhaps, the blood simply being an illusion.

He also tells them that the potion is an Elixir of Truth in case it comes in handy later.

--------------

When the party eventually explores further and higher up in the tower and encounters the pit trap, Kiven will pull out his rod of ropes and be ready to use it after Abraxxus flies over, in case there are more traps on the far side.

Blau checks out the water with his god-granted abilities and determines their use for drinking and unholy water. "The Lord has provided again. Trust in his guidance for our success." He checks out the pit and turns to the winged half-dragon. "If you would be so kind and ferry me across until we can rebuild this trap?"

   Abraxxus eyes Blaus for a moment and then nods. Gripping his shoulders he propels himself upwards and across the pit before setting him down. " There you are Rock Man. Anyone else need help? " He looks at Eya and Respar but seems to ignore the elves. 

Whether by the rod of ropes or by abraxxus' wings, the group makes its way over. Grumblejack presents more of a challenge, but searching the nearby rooms provides an answer in the form of a number of long and well preserved timbers. placed across the gap and tied together so the ogre' weight is distributed, and he's able to inch across slowly. It is fairly obvious he does not care for the experience.

A nearby room appears to have been used as a pyre for many of the inhabitants, with remaining ashes and bits of bone everywhere. Shortly after that you find another capture pen, identical in function to the one you found on the floor below, but this one appears to be in working order. Or at the very least the trap at the top is closed shut, and not budging in the slightest if Abraxxus tests it from below.

There is another courtyard here, it is lit by a large candelabra with a trio of continual flame spells, shining an eerie green light over the area. This area features another magic fountain that seems to endlessly produce water, although instead of Charon, this one features a trio of frog like daemons.

Nearby is a storage room filled to the brim with stone fragments. After a second look, it becomes apparent that these were once statues of demons and cultists displayed elsewhere, before being broken and then the pieces thrown into here. It is likely that only the fountains' enchantment and resulting protection against being damaged spared them this fate.

Another room features a massive four poster oak bed, large enough even for Grumblejack. Its bedding and canopy are almost entirely rotten away, but the heavily varnished wood remains intact, and the craftsmanship is exquisite.

Judging by the tools, whips, and collars found among the wreckage, the next room belonged to the temple's master of beasts. A mural on the wall showcases a pair of clawed bear like creatures being summoned and bound with iron plates around their necks. Three iron collars suitable for large animals are found intact among the wreckage. 

An antechamber is found with a rather interesting decoration. A man appears to have been nailed to the wall here by hand and foot. Most of his bones have fallen to the ground by now, but the ends of his limbs remain in place. Above the macabre display is writing,  “The Master of Acolytes, stealer of children.  Let all who would turn to darkness see his fate and return to the light.”

Beyond the antechamber is what was presumably the master of acolytes' bed chamber. But from the looks of things the knights were so especially enthusiastic about destroying this room that they knocked a hole in the wall. Light streams in from outside, and the Caer Bryr's aggressive plant life has invaded as well. Celarel calls out a warning before anyone enters this area, pointing out a pair of slimy green blobs almost hidden amongst the foilage. bones of various birds and other wildlife can be seen nearby.