Simon travels down several if the stacks finding them blocked.

Eventually he finds one that is traversable and enters. 

Upper Bastion

Simon emerges into a large room. 

This large chamber extends over the outer gauntlet of the main entrance and contains many former defensive measures. Arrow slits to the north allow outside light to enter, filling the northern half of the room with sunlight or moonlight depending on the time of day or night. Thick webs are strung between the walls and pillars.

Perception 11

Simon spots some large shapes moving through the webs and Toot identifies them as giant spiders. 

 Toot brings Simon back and asks him to check the other stacks.

 Soon Simon finds another open stack and scampers down.

West Upper Barracks

A fireplace is built into the west wall of this room. Hanging from a hook above its mantelpiece is a nonmagical steel shield bearing the symbol of Axeholm: a dwarven gauntlet clutching a handaxe. They could use the fireplace’s soot-stained chimney to enter or exit the fortress. The room’s other furnishings — cots, tables, chairs, and empty footlockers — are intact but covered in dust.

 Toot brings Simon back and tells the others what they saw.

 "I could climb up and feed down a rope."

 "I still think I could get through those arrow slits and come through the other side."

 Thomas thinks for a moment.

"Give it a go but return at the first sign of trouble. We have other options."

 Toot squeezes through one of the small openings in the wall.

She quietly casts mage armour on herself as she goes. 

Western Bulwark

This area contains seven ballistas pointed at arrow slits, a winch that raises and lowers the portcullis, and a stone staircase leading upward. Each ballista is equipped with five bolts.

Toot spots the winch and calls back to the others.

 Thomas reaches through and places a hand on her arm.

"Oghma guide your hand Toot." Casting Guidance.

 "Go on Toot, we believe in you!" (Bardic inspiration)

 "We will lift from the other side."

They gather at the portcullis and wait for Toot to attempt the lift.

 "Ok... here goes! 1...2...3..."

Strength 7 + 1 + 4

 The winch is stuck solid. "Sorry guys."

 "Plan B it is then."

Athletics 18

 Feldoran makes the climb and lowers down a rope for the others to follow.

 Once they are all up top and standing around the chimney.

"We should lower another rope down to make the climb easier."

She secures and lowers a rope into the chimney.

Athletics :

• Thomas 5
• Elandra 16
• Anders 16
• Toot 17
• Feldoran 20

They all make it safely to the bottom.

West Upper Barracks

A fireplace is built into the west wall of this room. Hanging from a hook above its mantelpiece is a nonmagical steel shield bearing the symbol of Axeholm: a dwarven gauntlet clutching a handaxe. 

 "Nice shield, anyone need one?"

 "No, I think we can leave it be Anders."

 "There are Giant spiders in the next room I think."

 "Well then. We had best prepare ourselves for battle."

 Feldoran makes a quick search of the room.

Investigation 6

He finds nothing of interest.

 Thomas hangs back and casts bless on Elandra, Anders and himslef.