"Progo agrees with Goraseth, sometimes the evil you know is safer the the evil you don't. Progo thinks we should approach quietly and see if we can spot any dangers where we can get to. Progo thinks we are safe from the ballistics in the kill slits from the dead being in there. Lets plan if the dead are not roaming by our way in, and if they are then mayne we explore chimney sweeping. "

"So, Progo, let's silently sweep the entrance first and see if there's anyone occupying the ballista rooms? Or would you prefer to go alone? I'm decent in stealth but no match for your skill."

Stealth roll in spoiler in case we go together:

Rayce will make on illusion of a halfling that sneaks up to the gate and then climbs in through the ballista slits about 10-20 ft ahead of the PCs.

The illusion makes no noise but the hope is it will get enemies to reveal themselves.

"Uh, right, Rayce, apologies, I didn't realise that you, too, are accustomed to move through the shadows."

Rayce smiles and winks back.

Tharanau hangs back and observes the outcome of the scouting mission. 

Ballista rooms are empty, no enemies there. The stench of dead is stronger than on the outside, you also do not hear anything from upstairs.

(The rope to climb up is still there?)

”I could climb in and check upstairs,” Tryn proposes in a hushed tone and prepares to climb through a slit (into A2) to check the stairs and upstairs. He waits for confirmation, however, before going off.

(how’s light inside? I suppose something is visible during the morning?)

Seen everybody slowly approching the stronghold, Gorasteh will follow, waiting under the murderholes. "being silent is not my thing" he is telling himself
Stealth: 11

Southern rooms of a22 are well lit, and there is dimlight in rest of a22. Room is empty, there are visible signs of the fight you had there. Most of spiders and fallen ghouls is eaten or taken away.

if you would be looking trough southern slits in a22 you can get a glimpse of the same ghostly figure roaming the same corridor as it did before. Other than its slight ghostly glimmer you can not see much else as it is dark inside. The foul smell is stronger, the more you venture in. There is some growling heard within the halls. You are not sure where is it echoing from but the sound assures you, that there are still some left within the axeholm.

If no close danger is seen, Seth is climbing the rope back in A22. He whispers "One of us should go without noise down the stairs and see how many Ghouls are waiting for us downstairs. With my large metalic armour, I am not the best one to do this.".
He is pointing at the Western stairs and adds: "What about we go down this way? Tryn did some recon already."

"Let's get back in where we can, Progo will do some sneak sneaking once everyone is in and have a secured way back out." 

Tharanau follows Seth back into A22... he cannot shake the foreboding feeling he's been having. Last night he couldn't find sleep, being woken by dreams where he got paralysed over and over again by ghoul attacks. 
"I am still a fan of the ballistas. Yes, let's go down there. " Tharanau agrees with Seth. 

Rayce will make her way into a22 and carefully down the stairs as suggested.

On the way, she looks for the dagger she had thrown and any arrows that might still be lying around

She positions herself at the top of the stairs and has her illusory halfling creep down and peek out into the room below. Then see goes down quietly and observes the room and listens at the bottom of the stairs. She then  has her illusion go ahead first into the room before continuing herself.

Rolls stealth 25, perception 13.

Tryn also sneaks down to A22 and peeks through the southern slits. He proposes to continue exploring into the corridor. If they can get to the main chamber, perhaps they could open the main gate and have an easier time to enter and leave should it become necessary. 

Stealth: 25 (crit)