"Goraseth, bring a few more legs, they seem to like it. I can try to hurt them with spells in the mean time." Tryn casts another Mind Sliver (for 1 unless a DC 12 INT ST is met) at one of the ghouls fighting over the spider leg.

Having finished placing the cauldron to block the stairs. Goraseth will follow Tryn suggestion
The paladin will also focus on his amulet to recover one spell slot (Harness Divine Power)

Rayce attacks a ghoul again for 3+2wrath=5 damage

Tharanau takes Fire wood from the fire places and shoved it under two of the unlit cauldrons. Then lights the wood with a tinder box. One in front of the tunnel and one close to the stairs. Then the one Rayce is heating up can still be used for one of the stairs. While the fires are burning, Tharanau returns to the arrow slits to watch the ghouls tear apart the spider leg. "What would I give to have a spell that could reach all those ghouls at once" He dreams of a fire ball. 
But even without that he again sets himself to the task to at least decimate these creatures before they enter a direct fight. (22 to hit for 8 dmg with ray of frost)

Tryn, your attack did not catch ghouls mind, as he was fully concentrated on eating :P
Rayce and Tharanus attack hit. 
Let's say that cauldron on the left will be heated well in 3 rounds. on the right stairs 4 rounds, and the one further away - at the tunnel at 5 rounds. 

As of this moment 2 zombies wander off from the chamber where they are sniped to the doors on the right./they did left the chamber and are not seen now./

Goraseth will go towards the right side of our room and listens carefully to hear any incoming ghouls

perception: 20

Tharanau shoots again at the ghouls below (15 to hit for 4dmg)
how many ghouls and zombies can he see now (perception 20)? 

Tryn continues playing mind tricks, DC 12 INT ST or 4 psychic damage.

Rayce gathers up lightning in her hands again and hurls it down as she continues to concentrate on the bonfire

18 to hit and 10+2= 12 damage

Progo is going to try to watch for anyone coming up the stairs on the side others tell him that lost site of a few, bow back out.

Tharanaus ray hits and that zombie spots him and starts going away to find his way up. But then Tryncaryn hits with his mind trick and ghoul then decides to smash its head on the pillar (and is destroyed) 
Rayces hits one hard and this one roars at her and goes out of the chamber (to the right doors)

3 of the ghouls that were in left part left the chamber using the doors that were on the left side of the chamber.

4 ghouls remains and feast on the spiders.

cauldron on the left will be heated well in 2 rounds. on the right stairs 3 rounds, and the one further away - at the tunnel at 4 rounds.

Goraseth you do not yet hear any, so that means they are definitely not close enough to attack next round.

Rayce keeps taking shots.

13 to hit and 2 + 2 =4 damage

Tryn also sees no reason to stop decimating the ghouls as long as they are distracted and he and his group aren't in any immediate danger. 

Mind Sliver INT ST DC 12 or 1 psychic damage

Progo watches from behind a cauldron and realizes he has a problem. "Hey Goraseth, quick question, how do you plan to tip heavy hot cauldron if anything comes up? Progo not sure Progo is preped to do such a move."

“Hummmm good question. I was hoping that with the strength of two of us it would work.”

DM : would that be enough ? 2 characters strength?

Your attacks hits, remainig ghouls in the chamber goes after the other ghouls that already left and went out of the chamber, two left and two right. New band of ghouls (6 of them)  that were assembled beneath your chamber closer to the big doors (you could not have seen them earlier because they were under you) are now also going after the rest. Right now they have reached the center of the chamber and are going to split in two groups.

/tilting the cauldron will be a strength check, made with advantage if someone helps/     

cauldron on the left will be heated well in 1 round. on the right stairs 2 rounds, and the one further away - at the tunnel at 3 rounds.

Goraseth and Progo sees that one of the ghouls is already at the base of the left stairs.(not visible on the map yet but he is below the red circle on the map)

/i noticed tharanau did not go yet, so you can do two rounds/

"Progo ! I hear something. I might need your help to spill the oil!" Goraseth tells the half-orc. He will wait for the oil to be ready and the ghoul to get closer before spilling the oil.

Athletic with advantage: 25 (critical 20 !)

Tryn plays mind tricks with a new arrival (DC12 INT ST or 2 psychic damage) and hopes that they will be able to repel the ghouls. It looks like they will be approaching from two sides and the group will have to split to fight both, or even three, fronts. Another thought wriggled its way into Tryn's mind. 'What were those ghostly shapes at the far side of the lower chamber? They didn't seem to be ghouls. Is this place haunted? Perhaps, the real challenge in conquering this fortress still awaits.' 

Rayce will move towards the right cauldron ready an action to blast any ghoul that comes into her sight, waiting for the oil to melt. She also takes out her short sword again.

"Tharanau, Tryn, come help me push this over when it is time."  she says.

She still maintains her concentration on the fire under the left cauldron.

Tharanau looks up when Rayce calls. He has been thinking of all the possible ways to fight these ghouls. 
He quickly lets out two well aimed attacks in quick succession, unfortunately just causing mere scratches to these beasts. (17 to hit for 1 dmg and 20 to hit for 2 dmg).

He then joins Rayce on the right, but places himself half way between the two cauldrons (right and tunnel). How far are they from each other?