"If these delvers tell the future, then they are already prepared for us."  Rubin informs the old man.  "Have faith in your delvers if you believe so much in them.  Nothing we do would be unknown to them."

Beyond the door—

An enormous chamber with a twenty-foot ceiling has been carved out of the rock here. A lighted lantern rests on the floor near the center of the room. An odd array of stone monoliths — some upright standing stones, and others arranged in three-stone arches — stand around the chamber. Six low stone slabs are set against the walls around the perimeter of the room. Each holds humanoid bones, dressed in scraps of tattered cloth and rusted iron.  The room is easily 130 feet by 100 feet.

DM screen:

Jairus will check the room for traps and secret doors and mechanisms within his understanding, but tries to keep his distance from the bones and anything he thinks might be magical in nature, leaving it to more learned experts to explore those. 

Perception:

   18   

Investigation:

   18   

He also looks to see if there are any footprints, and how recent they might appear and what kind, how numerous, etc, to try to gauge how recently the room was entered and who or what went through, if any.

Survival:

   18   

Davian enters the room last, speaking to the old man just as he does. "Fear not mister, if the future can be told then your Delvers know that we are here and the outcome is already determined. What will be, will be. " To himself he thinks "Time is fluid, no event that hasn't happened is guaranteed. Is it?" His teachings at the glade spring to mind. As quickly as thoughts of home came they are gone again once he enters the grand chamber. The sheer size gives a pause to Davian's movement. He will remain near the group as Jairus searches for hidden traps.

Here's a map of the room you're currently in:

(The door on the left is the one you just came from.  Each square is 10 feet.)

Jairus, you find nothing amiss at a cursory glance.  There are a few tracks around the place, mostly one set of footprints.  They seem to have ranged around the room, probably studying the stones.

As you all enter the room and Jairus begins poking around, you hear a muffled chanting noise coming from somewhere in the room.  Before you can react, a figure appears from behind one of the two large conjoined stones near the middle of the room.  He finishes his incantation, gestures curtly, and a ringing cacophony descends on all of you except Davian (it's a 10 foot radius, since he lingered behind and Jairus ranged a little it would probably miss him).

Everyone but Davian, make a DC 13 Constitution saving throw or take 17 thunder damage, half on a save.

The figure is wearing robes apparently made of woven stone, and carries a glaive negligently in one hand.  He begins chanting again, magical energy building around him . . .

Initiative:

Larakh: 17

Jairus: 11

Kethra: 21

Tyde: 16

Davian: 22

Rubin: 22

Symon: 19

(Here's a picture of what he looks like:)

(Kethra, Rubin, Symon, and Davian are up.  Larakh (the priest) is about 40 feet away, and is partially obscured by the rock.)

His animal instincts take over again. Without hesitation, Davian starts moving towards the stone priest. A whirl of smoke obscures him for a fleeting moment and dire wolf emerges, running towards the priest. It launches at the chanting clergyman.

Bite Attack: 23 Damage: 14

(DC 13 strength save or be knocked prone)

21 Con save

Symon cries out in pain, his head pounding and his ears ringing.  The Delvers had been expecting them.  Instinctively he glances around for cover - but he needed to get closer.

Taking his full movement and the Dash action, he sprints to the far corner of the conjoined rocks - hoping to find cover while cutting off any escape of this mysterious priest.

CON save: 19

Both Tyde and Symon manage to resist the worst of the blast.  Symon dashes for cover, and ends up about 10 feet away from the priest.  Davian suddenly decides he's a wolf, and pounces on the erstwhile priest.

Strength save: 15

He manages to keep his feet, even with a hundred odd pounds of wolf being flung at him.

(Kethra and Rubin are up, need saving throws from Jairus, Kethra and Rubin)

Jairus’ Con save: 3

He takes half damage, noted on his sheet.

bRubin con save: 13

Rubin first takes two shots at the figure.

Attack: 18 Damage: 7

Bonus action Attack: 12 Damage: 4

He will then separate from the others and move to cover within the stones.  he would circle to where he would be able to get line of sight on the enemy, though remain behind cover until he has his next turn.

Both of Rubin's shots skitter off the rock the priest is partially obscured behind.

(Kethra is up, turn and saving throw)

(If Kethra can't post tonight by the time I log off, I'll do this turn for her.  Just to keep things moving.)

CON saving throw: 18

Following Symon's lead Kethra will run forward to dash so that she is taking cover at the smaller rock east of the three rocks bundled together, and still less than 30 ft away from the priest.

Edit: Thanks for waiting. Sorry.

With a dash you could get right next to him, if you wanted to.

Sure, I'll do that instead!