Skameros frowns at the results of Rudolfo's attempts.  He'll light a torch, cover his nose and mouth with one paw and try to burn the brown stuff away with his torch.

Yeah... since Skameros is doing what Beegred warned not to, the halfling will quickly step back from Skameros and the mold.

Skameros lights a torch.  His party realizes what is about to happen and back away at a safe distance.  Skameros approaches the mold, feeling the air turn frigid.  Once he's close enough to put the flame of his torch to the mold...

Skameros DC 12 CON Saving throw: 24.  On a fail, take 18 cold damage, or half on a success.

Skameros feels the warmth being sucked out of his body just as the flame winks out, the heat of the torch also stolen by this mold.  As the mold feeds, it grows in the direction of Skameros and the flame of the torch.  Skameros now finds himself standing in the middle of a 10 foot patch of this brown mold.

(Everyone gets the equivalent of a combat turn, ie: movement, action, bonus action, reaction;  as Skameros will have to roll another saving throw when his turn comes around again.)

Beegred to Grithik: "Wake up, man gnome! Mold doesn't like intense light. Hit that main batch with some Sacred Flame."

To Rodolfo: "Freeze-dry that mold on Sakmeros with ray of frost. Even if you hit him by accident, it will be better than that mold."
(OOC: Kind of like a fire extinguisher being used on a fire.)

Beegred will cast Gust of Wind. If possible, he'd like it blow around Skameros, but not directly at him.
(OOC: Don't know how effective this will be, and don't want to push Skameros away.
But maybe the spell will push the mold from growing towards us, or douse the torch, or otherwise keep the mold and spores away from the party.)

Grithik jumps into action and casts Sacred Flame at the mold on the wall next to Skameros.  Visually, the spell looks like fire, but it doesn't contain the heat of an actual flame.  The radiance leaves a streak of cleared wall where the sacred flames struck, without any further reactions from the mold.  

(Given time, the mold could be obliterated in this way.  It could be visualized as painting a wall a different color using a paintbrush, where the casting of sacred flame is one stroke of the brush.  However, Skameros is visibly affected by the mold and doesn't have that kind of time.)

(There is no mold on Skameros. Only on the tunnel walls around him.)

Beegred casts Gust of Wind, directing the gust beside Skameros and down the tunnel in the intended direction of travel, as a precaution to avoid having spores and other air born particles float towards the party.

(Orubis and Rodolfo can act)

Rodolfo yelps, "OH SHIT! I'll get you out above it Skameros, don't run!"

He casts levitate on him.

"I can do frost after that, but he seemed to need to be out of it right this moment"

Skameros stands there with chattering teeth

(Sure, why not!  The tunnel has a very high ceiling apparently.)

Rodolfo casts Levitate on Skameros, who rises 20 feet directly up in the air, well away from the patch of mold affecting him, and floats there.

(You can resume out of order posting, as Skameros will be safe up above for the time being.)

Rodolfo will try shooting a ray of frost at a patch of the mold: Attack: 23 Damage: 4

If it works he will continue until things are clear.

Orubis will march forward, casting word of radiance to hit as much of the mold as he can. 

9 on a dc 14 con save

Skameros bobbles and wobbles in the air

Beegred the leaf blower will continue cleaning up as the others disinfect.

Upon casting ray of frost, the mold instantly withers and dies, leaving the way forward safe.

Orubis leads them onward, slow and watchful for more of the demon mold. 

Skameros lowers a piece of rope down so someone can pull him along like a large furry balloon. 

After 4 hours of searching, Rodolfo is the first to spot a branching tunnel flanked by the serene faces of male and female deep gnomes and symbols depicting some kind of circle.

Yet, entering this new tunnel doesn't yet reveal Entremoch's Boon.  This tunnel also branches off in various directions...

Walking past a branching tunnel, Orubis notices a decent sized cavern filled with shattered bits of statuary and underneath the debris is an almost covered summoning circle.

(Your party has not entered the cavern with the circle yet.  Orubis just sees it from a short distance away)

Orubis calls to the others. “Hey, is that what we’re looking for?” 

Rodolfo says, "Oh! This is interesting. I'd say that we're close, yes."

He looks around, "Before we look closer - anyone see any of the nasty mold? Or anything else weird?"