Titaani raises her hand at Matilda's question. "I can take someone with me too."

(The map is confusing, sorry.) All of the towers - the central tower as well as the turrets - are windowless above the first floor. But the ceilings are high in the turrets, and the windows tall and somewhat elevated.

Your choices for exiting via a window may be limited to:
1) climbing out the missing window under the stairway and clambering up a waiting rope (probably after untying Strongheart, unless you have more rope.)
2) break a different window, followed by a roughly 10-foot lateral jump, teleport, or other means, across the void, to a balcony. (The balcony has a railing, so any jumps would involve grabbing the railing and holding on.)
3) ??

(Sans safety precautions, the more risky methods may require some rolls...)

OOC:

DM, is my original proposal feasible?

I send Rizzo to untie the rope from Strongheart, but leave it anchored to the structure. Rizzo brings the rope to us and we use it for protection so we don’t fall into oblivion. We can swing across and climb up the rope to safety and Rizzo will shuttle it back to the next person.

Titaani’s teleport and Pud’s vortex warp could serve as additional safeguards. 

(Yes - the untied rope would extend down to the empty window frame in the turret below. Each person would just need to climb the rope to the stairway.)

Ben:

"Right, let's try that," says Ben, finally getting the internal/external architecture understood, "Then we can try and save Strongheart."

Thinking a moment, he adds, "Do we need to put Strongheart's name and your other companions into the Book before we leave this area, Elkhorn?"

Matilda nods but can't quite ease the fluttering feeling in her stomach that they are dooming Strongheart somehow......still there is little else to do but agree.

"I have the book. I was planning on taking it with us." Horatio offers in reply to Ben. 

Unless you have other business first, you begin to act on Pud's plan:

Rizzo is sent to untie the rope from Strongheart, leaving it anchored to the stairwell above. Rizzo carries the end of the rope to the waiting party in the empty window frame below.

Each person must grab the rope, swing out, climb it, and scramble onto the stairway. Then Rizzo will return the rope to the next person.
For seasoned adventurers like you, we will set the DC very low: Make a DC5 Athletics check, with natural 1 an auto-fail.
Pud also recommends using the rope "for protection" by which I'm guessing he means tying it around yourself first as an added precaution? This might certainly help, provided the rope holds...

When you're ready, go ahead and roll your athletics check. Also let me know if you take any precautions first, and what your plans are if you or one of your comrades fall...

(( Horatio Athletics 16 ))

(( Can Horatio offer Help to each other character one-by-one as they make the climb? ))

(Not in the mechanical sense, but if they miss their roll by 1 or 2, they may be close enough for Horatio to try to grab from above.)

Horatio easily makes the climb out the window to the top of the stairwell. Rizzo delivers the rope to the next person.

Pud stays back, nervously watching as the crew begins to make the climb. He reassures them as they get in line to wait their turn.

”Don’t worry. If you slip I’ll snatch you up with my spell. And once we’re done I’ll have Rizzo tie up Strongheart again. We’re not leaving him out there.”

Ben:

Athletics Check:  19

Ben climbs up and prepares to anchor the rope for the others.

Horatio and Ben have scrambled out of the tower and up to the top of the stairway. Horatio watches for anyone who might slip from the top end. 

Pud waits, preparing to rescue anyone who falls that Horatio can't help.

Elkhorn goes next. "Here we go!" cries the aged dwarf. DC5 Athletics check: 6

Matilda and Titaani are next?

Titaani gives Tiny a kiss on his forehead before dismissing him with a puff of purple smoke. She wraps the rope around her waist, tying it into her best attempt at a knot, and attempts to get across. 

Athletics check: 11

Matilda does her best...

2

Pud watches as everyone makes their way. He flinches as Matilda, of all people, seems to struggle with the climb. Once everyone is safely on the other side, Pud climbs as well and rejoins his friends. 

“Thanks for getting the rope, Rizzo. Now go and tie up Strongheart so he’s safe and sound.”

Titaani slips and nearly loses grip of the rope dangling above the bottomless maelstrom, but manages to save herself.

The last to go is Pud. (Go ahead and roll, Pud!)

The others find themselves on the stairway outside the door to one of the exitless upper turret rooms where you found a gem, earlier. The stairs lead down to the marble hallway just north of the Rug of White Roses. Presuming Pud makes it across safely, where to, next?

Pud flinches as Matilda nearly loses her grip, but she manages to save herself and make the climb. Pud receives the rope from Rizzo and climbs up to his friends. 

“Okay, Rizzo. Take the rope and tie up Strongheart so he’s safe. Thanks, girl!”

Athletics check: 16

Ben:

”Do we know if the entity holding the horn and touching the time frozen person needs to say the name?  Can Rizzo speak?” asks Ben, intent on saving Strongheart now if they can.

“Uh…Rizzo can’t speak like normal people. She can only speak to me…but only in my mind. Kinda like how I can send you guys messages in your mind.

She’s really chatty. And a little sassy.”