Grenk dex save 12, with advantage if its magical 29 , also he's a goliath so is resistant to cold damage.

 Grenk shivers a little, "Tid bit nippy," he mumbles more to himself and then stands at the edge of the pool.

Mal Dex Save: 18

Mal grumbles as she shoves her tools back in her backpack, swearing that once she gets out of this place she will be replacing them. Then she will move over to the black pool and take a look around it for any hints.

Perception: 13

(it was magical, so Grenk took only 1/4 damage)

Mal looks at the pool.  The liquid is still as glass. Looking in the pool she sees a reflection...but....its not the reflection of this room. It's the reflection of the large basalt column you saw at the entrance of the tomb...as if you were staring into a pool surrounding that column.  A bird flits past the scene. A small swarm of bugs lazily goes by.  You're suddenly reminded of the intense heat and jungle life that awaits you once you exit this place, that now suddenly you shiver with the cool atmosphere around you.  You also think about how long will you yet need to march back through the forest to return to civilization before your quest is truly done. The thought gives you no comfort.

(At least another 3 months of online campaign!!)

"So any of you magic inclined beings want to see if this pool is magical? As I think we might have finally found our way out." Mal says.

Clearly it is magical, Badger scoffs. Perhaps this is what is referred to as "the pillar and the pool", which those stones are supposed to activate. It might be worth tossing one into the pool, as Grenk suggested. Who has them anyway?

"Obviously I am no expert but shouldn't we discern the effect of this pool before we go tossing things inside of it? If this truly is our way out I would assume it is locked magically somehow." Mal says.

Grenk will touch the side of the pool but not the liquid. 

Psychometry history 8

"Good question about the beads orbs, whatever.  I'll be the test subject."

(I believe you have advantage on that roll if you’re touching the object, yes?  I can’t tell if you did cause I’m on mobile.)

I did not roll advantage 8

Well 10 is better than 8

I may be able to learn more about it, but it will take some time. Badger prepares to cast a ritual spell to identify the nature of the pool, if no-one does anything else first.

"It seems we have all the time in the world at the moment." Mal says as she leans against a wall and slides her back down to sit on the floor facing the entrance.

Grenk gets obscure images in his mind, of a foot stepping into the pool...ripples....a column growing up out of it.....a hideous witch face....and then the undead face of Acerack....glaring directly into his mind. 

Badger casts his identify spell....casting a special marble into the liquid will cause it to form a copy of the basalt column outside. It will remain in place for 1 hour. Anyone who touches it is teleported outside the tomb. There is no information of how to enter from the other side. 

With this new found information you all stare at the pool.....in silence....

Badger starts whistling a tune, while twirling the ends of his beard with one finger

"Any thing of use?" Silas question as he dust off the ash from the fire. 

Mal finally speaks up, "So I assume we don't have a special marble to throw into this thing? Or if we do have it, someone want to toss it in, so we can get out of there."

With a start, Badger suddenly begins fumbling through his pouches and then withdraws a smaller pouch containing the twelve grey lustrous marbles. Hmmm, funny, I don't remember grabbing these. With a shrug he begins handing one out to each of his companions.

(Looking back through the posts, I don't think anyone actually claimed them)

Tossing a single marble into the soup seems to do the trick.  It spreads out, as if dissolved, and coalesces near the middle where a column seems to grow forth out of the center of the pool.  A moment later a basalt column has formed in the middle of the black pool. The civilian leaps into the pool and touches it....vanishing. 

"Alright people let's do this, everyone through the black portal of death." Mal will wait for everyone to go through and then step through herself.