The Valley of Ends

Gotch stands back and watches.

Well with two ropes we could make a bridge out of the bones, but how to get hold of the artifact? 

Onyx will keep an eye open if anyone is watching them: perception 10

Onyx sees nothing out of sight but someone seems off. There's sounds of thunder in the distance but not a cloud in the sky. Raynor and Onyx try to throw one of the joints into the liquid sea. It impacts unseen ground but after a moment, it seem to dislodge itself and floats by the current back to the edge of the pool. Lyrant continues trekking through the silvery liquid, it comes up to her chest for a few moments before she comes up. 

Do I know or notice anything about the artifact? It would’ve come from her world before it landed here, right?

Lyrant has never heard of such an artifact of Selune specifically. The artfacit is looks like a pearl-like model of the moon, about size of your chest, hovering about 10ft in the air. Lady Jasmine described them as Tears of Selune but those are typically stars seen that follow the moon in the sky some nights. 

Selune worship exist across many planes and the artifact could have come from another plane.

Lyrant watches the artifact become flat as she apporaches and lower itself to Lyrant's level, just hovering there.

Lyrant checks for any kind of traps, and if she determines there are none, she will carefully take the artifact. During this, she keeps her focus on the connection with Selûne.

After a moment inspect, Lyrant reaches out and grabs the disc like object. The Moonfire underneath slowly fades away as if being soaked into the ground before a voice speaks in Lyrant's head.

"Child. If you hear me, Knights are approaching the city. Run now! Even without the relic!" Lady Jasmine's voice echoes through Lyrant's head and only her head. Lyrant recognizes this as Sending. meaning you can speak and she can hear you. 

(Add Full Moon Relic to inventory)

Lyrant snaps out of her trance, blinking and turning back to her companions. “The Knights are approaching. We must leave stealthily.” Replying to Lady Jasmine, “Thank you for the warning. We have retrieved the relic and are coming back.”

(If it’s your homebrew item, I’m not seeing it)

Onyx will grab a handfull of dirt and qickly puts it in a pocket, not bothering wasteing the time to find a tin in his bag. But he will take a second, to try to break a fang out of the naga skull. He wont be very delicate and uses his hammer to try to do it:

Another Sending come through "Knights arrived city's edge hours ago. Someone blocked Sending until now. Do not try to hide, run. Knights slow moving but powerful," (What you say immediately after receiving a sending will be sent back to sender)

Added as a custom item to Lyrant's character sheet for now.
Also the party has a compass to this city already
Add "Broken Bone Naga Fang" to your equipment as a custom item. 

Running up to Lyrant "Do we go the way we came or another route?"

We need to cross the river sooner or later anyway. With the land as it is, we may strand on the wrong side of the river for several days. I think we should try to use the way we came.

Lyrant will repeat “Thank you” as her response to Sending, then say to the party. “The Knights arrived at the edge hours ago. They’re slow but powerful. We need to go quickly. She will cast Guidance on Onyx. “Can you find us a way out without getting caught?” 

If he does roll, Lyrant will help for advantage.

((For future reference, Lyrant is bad with stealth and literally has disadvantage from chain armor. I’ll defer to one of you if we ever have a situation like this.))

Retracing your route will get you to the city edge's in about 4 hours, around sunset or night time. 

Survival checks if you want to try and figure out a new route. 

Gotch is ready to move.  He defers to Onyx as well as their scout.  "Back the same path may have less monsters, since we just came through there, while some other path may be quicker." He says as he glances to Onyx.  "Up to you though if you can find us a better way out of this place.  I can have my familiar scout from the air, or ahead if we go back into the sewers."

Retracing our steps.

perception 18

With Onyx in the lead, the party retrace their path back to the bridge then sewers and with the map, make their way through the sewers to the city's broken up as the sun disappears over the edge. All the while the thundering sounds grow steadily louder despite the progress the party makes. The party scrambles for the mountain up to the plateau they rest on the night before, reaching it exhausted from the rush. From the plateau, the party seem a wall of torches moving like a slow wave across the city.

From this distance, the party can make out heavily armored humanoids marching in formation across the city. The line breaks once in a while as parts encounters obstacles like building but quickly find the line reformed. For some reason, it seems unnerving to watch this wave slowly making it's way across the city. 

What do you want to do now? It's around midnight now, continue would cause exhaustion to the party. 

"Let's set up camp." Gotch suggests.  "No fire though..." He adds in, giving a slight shiver as he looks back towards the sea of torches below.