(Assuming that killed the last rat) Tresvar looks at the bloody armor covering her legs,, and says to the group-  “I probably should take some time to get this armor in a better shape before we move on- ok if we stop here for a bit?   If any other rats are about maybe we can convince them to leave us alone with some of these rat carcasses. “

 Pulling off her greaves, she does some bandaging of her wounds and adjusts the straps.  (Takes a short rest) 

5 hp recovered…

“I’m ready!” She says, although it seems like she’s still fairly hurt. 

"Let´s go on then." Serena says to the others, staying close behind Tresvar now, readying her crossbow to be better prepared when they next encounter trouble.
Perception when needed:3

Tresvar will lead the group.  She lights her lantern and hangs it on her hook if dark enough to be needed.

While Tresvar repairs her armor, Banjo pulls out his spell book and spends the hour preparing sleep again and steeling his mind to cast again.  (Arcane Recovery to restore one level 1 spell slot)

Taking a short rest to dress wounds and recover spells, the party has a chance to look around. They are on a sandy ledge overlooking a subterranean gulf of darkness to the west. The ledge is wide but rough. Sand, rocky debris, and the bones of small animals cover it.

Among the rubble is an old ring of stones that contains (and is covered by) the accumulated ash of hundreds of fires, though no fire has been lit here for a few years.

A rough-hewn stairwell zigs and zags down the side of the ledge, descending into darkness.

Tresvar searches around the ledge and fire pit for anything of interest or value before we move on, then she starts steadily down the stairs 

10 investigation.  

"As I can see just fine in the darkness, perhaps I should lead us down?  With luck I may spot the next batch of rat-beasts before they can spot us," Banjo offers.  Repeatedly finding himself on the front lines of monster combat has apparently done little to temper his enthusiasm and positive outlook.

Perception to look out for traps or ambushes: 12

“Ok… but be careful!” Tresvar says

The 5-foot-wide stairs that descend from the landing are roughly carved. They aren’t dangerous to traverse, however, except that combat while on the narrow path can be risky. Three small landings lie along the route. 

As the party continues down the switchback stairs, the morning light offers glimpses as a fortress emerges from the darkness. The subterranean citadel, though impressive, seems long forgotten, if the lightless windows,cracked crenellations, and leaning towers are any indication. All is quiet, though a cold breeze blows up from below, bringing with it the scent of dust and a faint trace of rot.

Link to Image of Party descending the stairs

The party descends, and sees more of the courtyard. 

As he enters the courtyard, Banjo notices an unmortared edge around what appears to be a trapdoor in the floor.

He wonders, how it works...

Link to image of party in courtyard.

Banjo slows and signals back for the others to stop.  "Let's slow it down now.  There's a trap door up ahead, and what looks like a door into the tower.  We might be able to go down, or forward.  Any preference?  I'm going to go have a closer look at the trap door...".  Banjo will cautiously approach the trapdoor.  If the mortar looks too loose (like the whole thing might collapse, he will be ready so skedaddle out of there.  Investigation 13

"We're supposed to find Lady Kerowyn's children, so perhaps the way that they took?" That said, she had no idea where they could have gone. She looks at the trapdoor Banjo spotted. Does it seem like something one is likely to notice, or a very well-hidden door one is more likely to miss?

Serena moves forward to help Banjo with his investigation. "The placement of this trapdoor suggests it is a trap-trapdoor."
Investigation:23

Banjo's investigation reveals that the trapdoor is in fact a trap. It is also larger than he initially thought, with much of it concealed. It effectively stands in the way of those wishing to get to the wooden door to the tower. Further investigation shows it to cover a 10-foot-square pit. A 2-foot-wide catwalk on the west edge allows access to the door.

The trap seems to be triggered by someone stepping on the trapdoor such that they would fall to whatever waits below.

Image of pit trap area in courtyard

 Assuming Banjo shares his findings. "So we use that catwalk then, and perhaps we could even use that trap against the stupid goblins in some way." She says encouragingly.
Serena then cautiously moves up to the door by the catwalk, examining it for further traps and checking if it is locked. Stealth: 13  Investigation:18

"Yikes," Banjo remarks when he realizes the extent of the trap.  He takes great pains to point it out, including where the edges and safe catwalk are.  "That could have been bad."

"Actually, Serena, I'd hazard a guess the goblins are well aware of this.  Its a bit... well-engineered for goblin work, but this sort of trap is straight out of Festuzio's seminal work, Pit Traps, Snares, and Falling Rocks: A Guide to Goblinoid Home Defense Tactics.  Most likely, they built this trap.  Though I like the way you think.  Perhaps there is a way to turn the tables on them."

After a pause as they skirt the western catwalk... "Strange that there is no fresh sign of goblin activity.  Serena is right... we should try to be quiet."  Stealth 21

"I guess the goblins could have built this trap Banjo, but it seems like it´s part of the original structure, and that was built by dragon cultists right. Anyway, let´s see if we can use it in some way later on." She says and glances back smiling at the others before returning to her work with the door.

The door is unlocked and appears free of traps.

"Ready? Here...we...go." Serena whispers to the others before quietly opening the door, crossbow ready. Perception:16

The door swings open and each member creeps along the catwalk and into the room beyond.

This circular area is cobbled with cracked granite, upon which sprawl the bodies of four goblins, apparently slain in combat. One corpse stands with its back against the western wall, the spear that killed it still skewering it and holding it upright. Three wooden doors lead from this area. A hollow tower of loose masonry reaches thirty feet into the air, but the intervening floors and stairs are gone, except for a couple of crumbled ledges.

Link to Image of party in Tower Shell