Lost Lab of Kwalish

Altar

This block of strange material glows with an inner light of opalescent blue, owing to the missing components of the Infernal Machine of Lum the Mad wired into its workings. There are three such components, each a deep sapphire blue. Removing one component safely requires a successful DC 14 Dexterity check using thieves’ tools, jeweler’s tools, or tinker’s tools.

In addition, Tarnhem’s flaming whip and lightning-imbued longsword have also been worked into the altar.

Tetrevess' mage hand pries at the blue stones and at the weapons, but fails to dislodge them.

<ruling: mage hand cannot remove any objects if interest in the altar. As they have a DC for sleight of hand they don't line up with the spell's description >

Tetrevess considers the issue and concludes it would be very dangerous for anyone but the original owner of the magic weapons to attempt removing them.  He also correctly assumes the blue stones are the powerful artifacts the adventurers seek.

Pentival responds to Gravity: "The altar is the means by which the acolyte of Vecna siphon power from the balor trapped within this tomb.  We must send the balor back to the Nine Hells and destroy this vile place before the power they take from him combined with the power if those stones creates an unstoppable force of evil.  My brothers (metaphorical) gave their lives to prevent the evil power if that fie d from infecting our world.  I will not allow their sacrifice to have been in vain."

Getting back to the chest:

The party retrace their path through the tunnel to where Sam left the oak chest, near the tunnel entrance from the long corridor (the hall of spheres, room 10).  Marltrh attempts to open the chest, but is unsuccessful.  With a loud knock, Tetrevess opens the vessel by magical.means. The oak chest holds 278 pp, ninety-seven small gems (worth 10 gp each), and a peridot (5,000 gp).

From across the great corridor, where the subtle tacks left by the oak chest as it was dragged over the unfinished floor disappear into the tunnel from which Sam pulled it, arise the sounds of clattering bones.  Soon the noise grows to a roar as a skeletal swarm pours into the hall of spheres from the opposing tunnel.  The sound if bones knocking together is so cacophanous that it leaves you deafened. 

<mechanical.note: the swarm can occupy another creature’s space and vice versa>

[Side note: Moghaddam, the architect, definitely knows where he was keeping Nolzur captive.  His blood was an essential component of a key feature of the design of the tomb he designed and the construction of which he is overseeing.  That said, he won't immediately pop up and look for people hiding down there, so you can use it for a short rest.]

<This really is a spoiler, read at your own risk>

Swarm initiative 6

roll initiative just because, but you can also just go ahead and post actions at the save time.

Gravity: Initiative 14

(Gravity's Turn: Round 1)

Gravity will examine the movement and characteristics of the Skeletal Swarm to determine its combat strategy and find out if it has some kind of vulnerability when she creeps closer to the chest filled with money and gemstone.

Intelligence: Investigation 7

Sam initiative 6 

“we need to get to the Balor now yess” then seeing the swarm “oh for **** sake, plans”

Gravity recalls the words of an ancient proverb: "Sticks and stones may break my bones..."

Gravity will scratch her head while pondering over the meaning of the proverb and watching her companions when they prepare themselves for another combat encounter. She stares at the mechanical guide 'Logan' with an expression of uncertainty and suspicion, finally she asks him if he can interpret the meaning of the puzzle. She seems delirious.

Initiative: 20

((We have not rested, correct?))

No rest yet.

We decided to open a chest first, it seems. 

4 initiative 

You can all just post actions. 

This thing is not much of a challenge. I'm honestly surprised if it will even get a chance to attack anyone.

Also, correction:  You're only deafened if and when the swarm occupies your space.  Earlier I wrote it like it was an area effect already impacting you; this is not the case.

Ana will hide behind the nearest pew. Hide: 22 

Gravity attempts to boost the spirit of her companions by saying:

"Look at this fragile set of bones! I bet my life that the skeletal pile won't sustain the flurry of blows, or the impact of a nicely placed kick. Where's that gargantuan bird when we need it? It's gigantic mass would've caused an impressive impact."

Tetrevess shoots a firebolt into the swirling mass of bones 

14 to hit

9 damage fire

The bones are charred in a blast of flame leaping from Tetrevess' fingertips. 

The swarm swirls toward the wizard, alternating between partially formed humanoid shapes and a chaotic swirling mass.

16 for 14 slashing.

Note: the swarm occupies the same space as the creature it is attacking.

<Sam, and back to Gravity.  Location of this encounter is the south part of the long room, the hall of spheres.  I guess you could flee all the way back down the winding corridor to the chapel,  if you want. In the hall of spheres, the party is coming from the left and bones are coming from the right. (1 round dps for this team is probably enough to pave this swarm.)>

<The green zone is OK for a short rest.  Actually, now that I'm writing this, I realize  the secret room to the northwest with the statue in it is probably a better and definitely closer  place, so you should try for that instead.  The gold star is Tarnhem the balor.  The passage near him is the one that leads to the safe room I originally proposed, where Nolzur was held,, but again, the closer and actually secret one makes much more sense.

You're still in combat, btw.>

(Gravity's Turn: Round 2)

Gravity moves away from the Skeletal Swarm without drawing too much attention while creeping closer to the northern part of the long corridor. She places a small flask on the floor of the chamber carefully so that the flammable liquid (Alchemist's Fire (Flask)) stored inside doesn't spill out of the container, and sends the flask towards the pile of skeleton with a kick.

Action: [Tooltip Not Found]: Catapult on the flask.

DC 14- Dexterity Saving Throw or the monster takes 13 Bludgeoning Damage + 1 Fire Damage at the start of each of its turns.

(Gravity was referring to the bludgeoning damage type while trying to inspire everyone.)

tetrevess calls out in pain as the skeletons overcome his magical protections..

Swarm dex save 22

Gravity's aim is true and the fiery flask explodes across the scattered bones, shattering them as they clatter to a halt.  The teidling artisans working in decorating the walls stop fir a moment to stare, wondering what's going on.

<the swarm was in the same space as Tetrevess last round, so unless he moved, he should also make the Dex save.  Apologies if I missed it. After that...>

<end of combat>