(You can absolutely level up, no need to wait for a rest. I need some more time to make a map for the last encounter, I think in around 12h I might be able to.)

(Ok, @Spark: Let's do an Intelligence check, with advantage from the background, to decide how much detail you remember from the map. You may add 1d4 from Guidance from Rizo to help you remembering.)

Intelligence check: 19

Spark remembers most of the details of the map, especially a large, deep crevice had caught her attention. The cave is sloped downwards towards the crevice before it sharply rises to the main section of the dragon's lair. A small water flow beaks through the northern wall and falls into the crevice. In the main section there is an elevated portion on which sits something that the druid referred to as the spirit gateway and a cave exit leads to a large platform outside the cave, though the Dragon Turtle ostensibly was swimming in and out. 

Map (brown numbers refer to elevation in feet):

"I hope we can get to this spirit gateway without having to face that dragon again."

(It looks like we just walk to the final chamber, or did someone plan to post something else and hadn’t have time?)

(I'm fine with just walking there, assuming we can get there safely.)

(Sorry, I had a packed schedule for a few days. Let's see if we can bring this back on the road.)

You manage to find some paper to create a copy of the map of the Dragon's lair and the few symbols that Rizo helped you to translate. With this and detailing your operation to Rizo, you finish a short rest. Afterwards, you set out to follow the tunnel towards the lair with Rizo leading the way with Light cast on his shield. Occasionally the tunnel stretches so thin that the chuul has to squeeze through but it does it so natural that you are sure it must have done it many times in the past. After a good half an hour walk the walls of the tunnel begin to rise higher and it opens into a large cavern. So large that you cannot see its extent and you wonder if this is the lair. But the druid's maps have indicated that there is no other large cavern, so this must be it. The floor slopes slightly down as Spark's map suggests. Fortunately, Spark was mindful to take note of the chasm that separates the two halves of the cavern, so that you are now extra careful to step downwards into the cavern. The cavern is almost completely dark, but to the East, higher than your vantage point you see flickering of very dim light. The light source is not in direct sight, and when you confer the map you realise that it must be behind the elevated section, just where you expect the gateway. What could this light mean? Is someone there? Does the gateway emit such light? Now, you just enter the cavern from the Western tunnel. What will you do?

Map: 

"Unless someone has a way to fly over the chasm, we'll have to cross on the north side.  I don't know if there's anything guarding this gateway, but perhaps I can create a sound on the south side as a distraction."

"I can try to scout ahead if that would be helpful."

“why not?” Rizo replies. “Do you expect anything here? I mean if there’s someone there they’ll see me coming because I don’t see anything without my light. If you scout, better stay out of our light.”

(if you want you can roll stealth and say where you want to go, and if you prefer we stay back or continue our approach to the chasm.)

(I'll assume Minty does scout, and I use his passive Stealth, but just around us not too much ahead.)

Minty melds with the shadows cast by Rizo's Light spell, while the group advances towards the chasm. As Spark pointed out, the only safe way to get to the other side is following the northern wall, so that is what you are planning to do. 

Don't mind this, just a few rolls.

Suddenly you hear the rhythmic thudding sound of hooves echoing in the cavern. But not horses, there's no metallic ring to it. 

A few more rolls, sorry, should have done that before, too. 

Then, suddenly 3 bolts come your way, one flies wide over your heads, a second thumps into Rizo's breast, and a third into his shoulder. Rizo slumps down unconscious and just as his Light wears off, you see two large bull-like skeletons jumping over the chasm towards Rizo's position. You can also see the outline of 4 short skeletons with rather large crossbows on the crest on the other side of the chasm.

(Roll Initiative!) 

Map (Mx - Minotaur Skeletons; Sx - Skeleton Duergar):

Rizo Initiative: 14

(Would Spark's Protective Wings (+3 AC) save Rizo?)

Spark's initiative: 8

Minty Initiative

10 

Quote from LaOtraVacaMorada >>

(Would Spark's Protective Wings (+3 AC) save Rizo?)

Spark's initiative: 8

 (Sorry, I’m ill and couldn’t post earlier. Unfortunately, the wings won’t save him from both bolts.)

Initiative order: 20:S2, 15:S4, 14:Rizo, 12:M1, 10:Minty, 9:S1, 8:Spark, 6:S4, 4:M1

ini chuul: 8

Two of the skeletons continue firing crossbow bolts, this time targeting the large chuul. It seems they just go for the easiest target. Rizo lays unmoving on the floor but a sudden spasm shows he isn’t done for yet, but precious little separates him from death’s door considering the mummy’s curse. One of the minotaur skeletons hews down his great axe on the chuul. 

Attack: 24 Damage: 5

Attack: 24 Damage: 9

Attack: 15 Damage: Unable to parse dice roll.

The chuul is peppered with two bolts that strike true and get caught by the heavy greataxe, too. It tears up and screeches in pain.

(Minty’s turn.)

Rizo’s death save: 5