You crawl into the second passage hidden behind the black circle and you immediately notice it's much longer than the first one. It first turns right, then right again and then it starts descending. There are a few more turns and you start to lose sense of direction but finally you reach the end. Here, as well, you're met with a wall of solid stone illuminated by your lantern. 

“Works for me.  Although, the red was mentioned alongside sacrifice in the riddle.  Perhaps if the black hole doesn’t work out, we should try bleeding in that room.  It seems a stretch, but it’s better than nothing.”

(Whoops, didn’t see that post)

"This one continues further." Lumiere will call to the others, checking the area as she goes down. Since the end is solid stone, as opposed to the earthy tunnel mentioned before, she tries to see if there is a switch or method to open the passage end perhaps. If she cannot find anything, she will backtrack to the others to let someone else have a look.

Investigation: 20
Perception: 28

(Finally, some decent rolls!)

Checking the wall and sliding your hand against it, you notice a small fissure in the stone. Following it and tracing the contours you recognize it to be a small hidden door. A bit more searching reveals a minuscule handle that allows you to open it.  

After Lumiere enters the "black hole," Ubogri gives Jerigg the end of the rope and walks over to the door between brown and purple. Without touching it, he inspects the door for traps.

Investigation: 18

After he inspects the door, if he finds nothing dangerous, he'll use the broken gargoyle statue arm to knock on the door in several spots.

You notice nothing particular on the door, and even after knocking on it you hear only a dull sound of stone hitting stone

(Since Lumiere found something, she didn't backtrack. Uborgi would be behind her still)

"I have found what appears to be a hidden door lever. I shall give it a pull to see if it opens a new path." Lumiere tells those behind her. "Perhaps backing up in case of something going wrong is best."

Falmo will creep down the tunnel and stand a good distance away from Lumiere.  He will then hide and Ready an arrow for any threats that might come through the door: Stealth: 24 or 25

Attack: 19 Damage: 12

Sneak Attack: 25  If the creature is surprised: 39

Whoops, that damage die should be a d6, rerolling: 10 6

The half-orc goes over to the door between orange and purple and inspects it in the same manner as the first door: checking it for traps without touching it, and, if he finds nothing, uses the arm to knock on the door.

Investigation: 28

I shove Lumiere out of the way and cast Mage Hand from 30 feet away and give the handle a tug. 

"Stop trying to be the dead!"

Ubogri examines and knocks on the second door, but this one isn't any different from the previous. At the same time Jerigg casts mage hand and while Lumiere is backtracking a bit opens the door in front of her. The small entrance opens into a big, bright room in front of you. You see what is obviously some form of temple area. There are scenes of normal life painted on the walls, but the people have rotting flesh, skeletal hands, worms eating them, and so forth. Yet there are also depicted various religious symbols of good alignment. There is a mosaic path leading between four rows of wooden pews that face the worship area. In front of the pews, a wooden railing divides the room. South of it is an altar in front of a tiered dais, on which sits a wooden chair. 

Falmo will examine the room, looking for any hidden riddles, doors, or maybe even treasure: 26 or 17

Finally going to remember I'm a halfling: 25

Going into the southern part you take a look at the altar. The chair is nicely carved and padded but seems unremarkable. On either side of the dais are large, free-standing large brass candelabras each holding five white candles. In each corner on the southern wall is a large white pottery urn stoppered with a brass and wood plug. Sprawled on the floor near the west wall is human skeleton in black chain mail that is badly rusted and damaged. The skeleton's outstretched arm points to a stone archway set in the wall. The opening is filled with opaque, bright orange vapors. On the opposite side of the archway you notice a small slot in the wall with the letter O faintly traced above. It's less than an inch wide and 0.3 inches tall. In front of the altar there is l is a block of strange material that glows with an inner light of opalescent blue. 

Ubogri looks over toward the black sphere, putting the statue arm away again. He waits for a second, then walks over to it and listens. "Anything?" he calls.

Quote from LordShadowthorn >>

I know, right?  I've rolled like four 1s and only rerolled this one.

 

I do the light ballbearring trick into the mist. Then I poke the end of my crowbar into the slot.