Quillary notices Spar doing this, and looks, too. A spider form could climb over and take a rope, and more importantly, be much more useful after. Then she realizes that Spar could carry a rope and do the same, without Quillary having to do anything. 

Hildigrim steps up to the edge of the crack, mumbles something magical and does a funny hand gesture. After a few seconds, he turns around. "Too far for my mage hand," he comments. "That means it's too far for me to misty step as well." He lifts one shoulder. "We could attach a rope to an arrow for me to fire, but I wouldn't trust it to hold safely."

Feldspar looks up, and only sees more empty space. If there is a ceiling, it is more than 120' up.

Hildigrim is correct. With the arrow pulling at least 40' of rope, the shot will lose a lot of its initial speed. The arrow might hit solidly enough on the other side to provide an anchor, but he couldn't be confident about it.

(Would a giant owl be able to carry a person? I think yes, but since the Giant Eagle is the canon flying mount beast, I want to check before committing.)

Quote from Mingofaust >>

(Would a giant owl be able to carry a person? I think yes, but since the Giant Eagle is the canon flying mount beast, I want to check before committing.)

(Large sized, and a web search brought up a lot of people using giant owls for mounts, so yes.)

Drusk notices Feldspar squinting upwards, trying to see where the ceiling is.
Hildigrim mentioned that shooting an arrow with a rope across the chasm might not work.
This gives Drusk an idea.
To Feldspar: "Hildigrim's maximum range with the bow is around 300'. You could ask him to shoot an arrow up (as long as he is willing to lose an arrow). If it falls back down, then the ceiling is higher than 300'. If you hear it hit something, that will give you a better idea about the height of this place."

Spar nods, and asks to see the arrow. She casts light on it and hands it back. She looks up expectantly.

Hildigrim accepts the glowing arrow, aims high ... and stops. "Before I almost assuredly forfeit another arrow," he says, lowering his arms, "let me see what Volo can see." He adjusts his footing, closes his eyes, and Volo takes off, flapping madly into the darkness.

While Hildi can only communicate telepathically with Volo up to 100 feet away, the wording of find familiar reads, "While your familiar is within 100 feet of you, you can communicate with it telepathically. Additionally, as an action, you can see through your familiar's eyes and hear what it hears until the start of your next turn, gaining the benefits of any special senses that the familiar has." Some DMs rule that the 100 feet limitation only applies to the communication. If the DM rules that communication and looking through Volo's eyes is limited to 100 feet, Volo can see 120 feet away, which means Hildi's vision through Volo is up to 220 feet (with darkvision). If it's higher than that, and (again) the DM limits vision to 100 feet, could Hildi ask Volo to continue flying and then return once he sees the ceiling and report how much higher he had to fly past 100 feet?

Perception roll for Volo in case you want one:

Volo is still within Hildigrim's mental range when Hildigrim relays some positive news.

The ceiling starts to narrow 150' up. At 180' up, the chasm continues upwards, but Volo sees a spot (to the "left" 50 feet) where the two sides are only few feet apart. Close enough for a giant spider or a humanoid with Spider Sliders to step across the gap, and be able to climb back down to the opposing ledge.

If someone is on the other side and the equipment there is not broken, it will not take too long to toss one end of a rope to them, and get the block & tackle setup working again.

Volo makes another circuit before returning. Besides some insects and normal sized bats, there are no creatures lurking in the space above the party.

Quillary turns to Spar. “If you would be so kind?”

While the others are looking up, Jorin is eyeing the distance as if he plans to jump it, but then shakes his head, "Just a little further than my best long jump, if you can carry me across, I can set up and strong anchor for the others with a rope."

Quillary shakes her head. "It may be that I should reserve my communion with a beast form for later, and we should rely on our new companion, instead," she nods in Spar's direction.

Feldspar assents to an ascent, as long as she can tie together four lengths of rope to hold onto (while the rest of the party holds onto the other end). She walks slowly, looking into nooks and crannies and keeping an eye and ear out for any surprises, and taking her time to walk slowly up, then over, then down to the other side.

Hildigrim has 200 feet of rope and several others have 50-foot ropes, so that should be an issue.

Quote from DirtyDogP >>

Hildigrim has 200 feet of rope and several others have 50-foot ropes, so that should be an issue.

(He has 100' and 50' of rope (post 5847), not a single coil of 200', but the group can carefully knot a few ropes together.)

Hildigrim does struggle a bit getting multiple coils of rope out of the Bag of Holding, as it is unwieldy.
A total of 200' of hempen rope is more than a cubic foot in volume and 40 lbs in weight, and there are a few tangles while laying it out.
Drusk to Hildigrim: "When we get back to Waterdeep, remind me to by several coils of silken rope. It is a lot pricier, but it is half the weight. We can afford to pay for the convenience, in case something like this comes up again in the future."

Feldspar crosses over without incident.
She did sweat a bit when taking a big step to cross the ceiling gap (3' wide), upside down and weighed down by an additional 40' of rope.
Fortunately the Spider Slippers magic gave her secure footing.

After Feldspar crosses over, she gets the block & tackle equipment working. The rope is securely tied off at both ends.
It is a bit uncomfortable crossing 40' over a chasm of unknown depth on a bouncy rope, but the party is safely across.

You find more tracks from the scout party, so they did cross over at this spot.
You also find the pieces of the rope that was previously used by the scouts to cross the chasm. The rope was torn to shreds, clawed or bitten through (not cleanly sliced like a sword or an axe would do). Although it looked like a beast mauled the equipment, the rope fragments and the block & tackle were pushed in a pile against the rock wall.

As the party is getting organized to continue forward, you notice something shiny 20' away (in the direction of the tracks you are following).
It is embedded in the rocks and pebbles, so you'll have to be standing over it to see what it is.
(It is larger than a silver dollar, but around that size.)

(We've kept moving pretty quickly even since the fungus, which is when daylight was cast on the pole. It has an hour duration -- how much longer do we have on it?)

Feldspar, once everyone is across safely and they fix the block and tackle system up to be able to return, says mostly to herself. "I'd say I'm earning that finder's fee."

She peers at the shiny thing and casts mage hand, sending it over to it. Can she pick it up?

Quote from rkmobius >>

(We've kept moving pretty quickly even since the fungus, which is when daylight was cast on the pole. It has an hour duration -- how much longer do we have on it?)

 

The Daylight spell expired as the party made it across the chasm. (There was more than half an hour of travel between the last fight, skimming through the drow journal, and reaching this chasm.)

Feldspar is able to bring the shiny object to her hand. It is a (non-magical) signet ring, signifying a unit commander of the Lord's Alliance.
(If you forgot what their sigil looks like:)

The interior is engraved with a name: Captain Paz Brannigan.
The ring is damaged. About a third of the ring loop has been broken off (and not anywhere around).
The ring also has dried blood on it. Some of it looks human. Some of it... not human.

(Paz Brannigan . You get me. Thank you. ;)

Quillary notes the ring, and then moves forward to continue tracking the scouts.

Quote from Mingofaust >>

(Paz Brannigan . You get me. Thank you. ;)

(There is lots I embellish, like changing the Citadel owners from Zhentarim to Lord's Alliance.
But in this case, that ring inscription is verbatim from the module.)

Jorin eyes the discarded ring, "Seems like we are on the right path.  And something mauled their equipment, so probably not the elf scouts we just encountered.  Some more beastly." He smiles excitedly as the party moves on.

The party continues moving forward.
After a few minutes, as you are passing through another cavern, there is some movement from behind a pillar of rock.
This cavern looks a lot like the one where you fought the Drow. (ie. I'm reusing that map.)

A pair of creatures emerge from hiding. They are 10' tall, resembling bipedal toads, although most of their size and bulk is from their enormous mouth and massive gut. Their skin is a queasy hybrid of shadow and flesh.

Everyone roll: Initiative and Perception (you might be surprised the first round by the creatures that were in hiding)

Drusk (rolls in Game Log) init: 10  perception: 11  (ugh all four d20 rolls were 10 or less... hope the rest of the party does better)