Ladrian

With a torch at the back of the group, Ladrian moves forward, trying to keep an eye at ambushes at the rear "I hate this place" Ladrian murmurs

As soon as Ladrian's torch sheds some bright light on the details in this small open area, the members of the party can see two corroded goblin scimitars lying on the floor near the pool of water. Additionally, the column of rock has a rather peculiar feature: several fist-sized holes extend deep into it. 

Rixton:

"Hold up, Snigbat," I say, stopping in my tracks. "What happened here?"

Investigation: 25

 DM screen:

Snigbat turns around and with a puzzled look on his face says, "What happened? Very old blades sit there for long time. Snigbat does not know what happened."

Every member of the party can see through the flimsiness of the goblin's answer. Snigbat seems to be hiding something. Furthermore, Andor, Ladrian, and Rixton can see the scimitars do not show signs of age.There is no rust on either blade. Simply put, the metal seems to have been eaten away by something. 

Andor

Fingers crackling with lightning Andor advances on the goblin "Enough with the lies, there is something here you want to kill us isn't there?  Tell us what it is and I might let you let you run, again. Otherwise you die right now."

Intimidation 22 

Snigbat stares wide-eyed at Andor's hands and begins to shake his head. Stumbling with his words, he says, "No...no...Snigbat..."

The goblin's eyes then become locked on the column of stone that stands in the middle of the room. The members of the party follow Snigbat's gaze, and they see something that is both unexpected and disconcerting: a thick, black gelatinous liquid begins to ooze from one of the holes in the column of rock...

• Initiative for Snigbat: 21
• Initiative for thick, black, gelatinous creature: 17

 Updated map:

Andor

Initiative 10

Nature 17

"Oh Snigbat, why am I not surprised, you stupid little goblin."

Andor begins to channel his energies in anticipation of battle. 

Rixton:

"Hmm...." I say, musing at this new development.

Initiative: 6

Nature: : 10

Vigan

Initiative: 7

Nature: 18

Ladrian

"You gotta be kidding me. Is that a walking dessert?" Ladrian says with surprise. After some consideration and connecting the dots with the clean swords without rust he then turns to Snigbat "Please tell me you didn't called a plumber?"

Initiative: 12

Nature: 15

Carrow 

"What is this new devilry" 

Initiative: 18

Nature: 8

And so it is that, within the span of a few seconds, the five adventurers realize that Snigbat has lead them into some sort of trap. The look on the goblin's face is evidence that he himself is terrified of whatever it is that is squeezing itself out of the rock. Three of the party members--Andor, Ladrian, and Vigan--have heard tales of this bizarre creature, and almost in perfect unison they call out, "Black pudding!"

Round 1 initiative:

• Five players, in any order
• Snigbat
• Black pudding

Andor

"My spells can't hurt it, we need to fire and move, as many arrows as possible! And someone feed the goblin to it." 

Andor unslings the crossbow from his back and fires into the mass of pudding before following his own advice and retreating  twenty feet back the way they have come, carefully skirting around the cavern to avoid the ooze.

Attack with crossbow 24 for 7 piercing damage

OOC I'm not 100% on the map scale, if Andor cannot skirt around the edge without provoking an AoO from the pudding then he will move down the other passageway a bit to create a more than 20' gap between them.

(@ Phadeout: Opportunity attack is possible only if Andor is/was within melee range (5') of the black pudding)

Andor's crossbow bolt pierces the ooze and then begins to dissolve quickly in the black pudding's acidic mass. 

Rixton:

I sheath my weapons swiftly and draw my last flask of oil from my pack. "I hope this doesn't paint me in the wrong light," I tell my comrades. "Oil is just a versatile substance." I unstopper it and empty the contents all over the black pudding. Then I withdraw from the creature, falling back to the southernmost part of the tunnel.

"Vigan, do your thing, but I can give you a crossbow after you light it up," I say as I reach from my bow and an arrow.

Carrow

The ranger looks from the black mass, then to the goblin and shakes his head. "Deceitful little rodents" he says under his breath slowly drawing an arrow to his cheek he points the bow at the goblin. Taking charge of his emotions he turns his attention to the more immediate threat, backing up to the south east corner of the chamber Carrow switches his aim and fires at the pudding. 

Attack: 18

Damage: 5 

Ladrian

Keeping his distance to the new enemy (ooze) Ladrian fires his shortbow!

Attack: 18 Damage: 6

Vigan

Swinging his torch at the ooze, Vigan attempts to set it alight, and do some damage of his own.

Attack: 25 Damage: 8 Additional Crit Damage: 3

 Snigbat immediately turns and splashes through the remainder of the shallow pool and then, sprinting at full speed, disappears into the darkness of the tunnel that leads north.

The black pudding seemed to flinch as it maneuvered itself away from the crossbow bolt and two arrows that pierced it. As the oozing mass makes its way down the column, Vigan strikes it with his torch, which causes the pudding to change shape rapidly as it reacts to the bludgeoning damage. As soon as he makes contact with the ooze, Vigan feels his arm burning in multiple places. | 4 acid damage

The black pudding then bursts into flames, taking 7 fire damage, while illuminating the entire room and emitting a dreadful smell. It then promptly reverses itself and vanishes into the column of rock from whence it came

(Round 1 concludes; all players may make their round 2 actions now)

Rixton:

"Show of hands, gents: Who wants to stick around to finish their pudding?"

I don't wait long enough for people to take it seriously.

"I didn't think it was that inviting either. Let's push on before we are faced with a second helping."

(Rixton jogs through the water to the J24, dashing if necessary)