In that case, Rhayna moves N to stay next to Kirin. She  takes the Wand of Viscid Globs (which was “conveniently” tucked between her belt), and she will target the Balor. (She hopes that, if it hits, at the very least it hits the demon’s torso, and restraints one of its arm.) (Rhayna will use her inspiration to roll with advantage.) Rhayna makes a small prayer before launching the glob from the wand.

Wand attack: 26

Pax sees the incoming Minotaur charging her while the other still attempts to gore her from the other side, and casts a quick magical shield which shimmers as it appears and sends both attacks glancing off without hurting her.  (+2hps to arcane ward)

A small black blob shoots from Rhayna's wand and strikes the Balor in its broad chest. Instantly the glob expands, forming larger and large black bubbles like boiling mud that spread across the balor's body and begin to engulf it, gradually hardening as they spread. Within seconds the enormous fiery demon is almost completely engulfed, with just half of each wing sticking out of the black morass, along with its head and its two hands, which still grip the deadly weapons. The balor thrashes about in frustration, and as it does so, Rhayna observes that whenever any part of the black mass extends into the range of Dawnbringer's light, that it instantly dissolves. With a roar of fury that causes fire to belch from its maw, the demon attempts to relatiate against Rhayna, although without the ability to swing it's arms, the strikes are more clunky than before...

Balor v Rhayna:
Longsword Attack: 15 Damage: 25 slashing plus 15 lightning damage
Whip Attack: 24 Damage: 14 slashing plus 12 fire damage (and a DC 20 STR save or be pulled up next to the balor

Pax is next. Start the turn with a DC 13 CON save or take 7 necrotic damage. Pax also has Bardic Inspiration (d6)

Map unchanged except for Rhayna is 5' further north.

For now the Balor is restrained. The light from Dawnbringer doesn't even cover half of one of the balor's squares, but there is a risk that if it gets any closer that the entire blob may dissolve and the balor will be free.

Rhayna holds her breath as the small blob shoots from her wand, until it hits the Balor square in his chest. With both arms up, she yelps "Yes!!" Then, she holds her breath again to see if the wand is true to its name, and as the Balor is engulfed by the very sticky black morass, now she jumps with joy. "Yes!! Yes!! It worked!!" But her elation is short lived for the Balor finally has its sight on her. Even though the huge fiend has been restrained by her wand, it is still a more than a formidable foe. The first attack hits, and she is able to resist being knocked down by a thread. Then the second attack also hits, the Cleric goes down, and she is dragged next to the demon by its whip.

(According to the text Unconscious one auto fails a STR and DEX save. So I guess I still roll for CON save? Rhayna CON: 18)

(Reminder : Any creatures that have been ending their turn in the storm should be making a Strength saving throw or take 2d6 bludgeoning damage, I think this minotaur close to me has had a couple turns in it now.) 

Pax glances towards Rhayna as the priest goes down, then back at the creatures all around them.  She grimaces and then holds out her hand.  A lash of black shadows whip across the space between them and a bit of energy flows into the girl.  (2 hp's gained from Healing Light feature)

Then she unleashes three blasts of arcane energy at the minotaur still in the storm. Eldritch Blast   (disadvantage for ranged in-melee countered by advantage for reckless attack)

Attack on Minotaur2: 15 Damage: 14 

Attack on Minotaur2: 19 Damage: 14 

Attack on Minotaur2: 22 Damage: 13 

(Forgotten CON save!! : 28 vs DC 13 ) 

Pax: By the powers, you're right! I did it for Round 3, but not for Round 4 as I thought the minotaur would be clear, but one of its squares is still mostly in the storm, so that counts...
Minotaur2 STR save for Storm Sphere: 21 for 10 damage

Rhayna: Yes, thanks for the CON save, I tend to forget to ask. Rhayna resists the stinky demons' stink. Confusion drops when she falls unconscious.

Rhayna's eyes flutter open only to find herself laying at the feet of the giant demon covered in hardened black goop. Fortunately, it seems the demon doesn't realise she is awake. Pax's second spell blasts the weather-beaten minotaur, knocking it down. The bull-headed beast falls over with its head inside the storm and the rest of its body laying on the cave floor.

Modron death saves: T 2, M1 4, M2 10

Kirin is next. Please make a DC 13 CON save or take 9 necrotic damage. He is concentrating on Bigby's Hand.

MAP:

 Round 4: Kleve 22, Bulezau 20, Kaylyn 17, Sekkar 15, Vizeran 15, Minotaurs 13, Rhayna 12, Balor 11, Pax 8, Modrons 7, Kirin 5, Dretches 3

Extra: Modron CON saves v 9 necrotic damage: T 21, M1 4, M2 6
Death save count: Tridrone has 1 pass. Monodrones each have 1 pass/1 fail.

Con Save: 21

Concertation Save: 7

"Go away," Kirin gestures with his free hand and sends Bigdy's Hand to strike the Bulezau next to him, "You're giving me a headache, let me give you one as well," Kirin casts Mind Sliver on the Bulezau as well. 

Attack: 16 Damage: 21 Force

Int Save: 17
Damage: 8 (half on successful save)

The over-sized magical hand floats up and over Kirin's head, clenches into a fist, and slams down on the goat-headed demon, squashing it to the ground. Pus explodes out of the numerous carbuncles and boils on the creature's skin, and drips off the spectral hand as it lifts off the ruined corpse, which momentarily melts away into a pool of ichor.

(Kirin: Would you like to nominate a new target for Tooltip Not Found, or would you prefer to choose a different action?)

Trying to find Tool Not Found is caused problems. 

Kirin will target his Mind Silver at Bulezau #1 while shouting, "Drop the storm! We need space!"

I would like to declare that at the start of Bulezau3's turn, Rhayna will use her Halo of Spores on it. (B3 CON Save DC18 or take 4 necrotic damage.)

(OOC: Can Rhayna use Mending to help the Modrons?)

Pax glances towards the academic, "I can blast one every few seconds while I keep it up!  Try to use it to your advantage!" 

Bulezau1 INT save v Mind Sliver: 11
Dretch4: Fetid Cloud
Kleve CON save (DC 13) v Rotting Presence or 6 20
Kleve CON save (DC 11) v Fetid Cloud 22
Kleve v Balor:
Bite Attack: 15 Damage: 7 piercing plus 7 necrotic
Claw#1 19 Damage: 13 piercing plus 8 necrotic
Claw#2 28 Damage: 12 piercing plus 8 necrotic
Fire Aura: Kleve takes 12 + 14 + 11 fire damage (resistant)
Bulezau1 v Pax: Barbed Tail Attack: 5 Damage: 13 piercing plus a DC 13 CON save or be disease/poisoned
Bulezau3 CON save (DC 18) v Halo of Spores 10
Bulezau1 v Sekkar: Barbed Tail Attack: 23 Damage: 6 piercing plus a DC 13 CON save or be disease/poisoned

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The last remaining Dretch shuffles toward Sekkar and unleashes its own smelly fart cloud. The goat-demon beside Rhayna finally succumbs to her own cloud of contaminants, and it falls down and vanishes in a splatter of ichor, leaving only two remaining which are still trying to hit Pax and Sekkar with their barbed tails.

Meanwhile, the death slaad moves in to attack the Balor. Whether on it's own volition or under instructions from its master, the slaad seems to have weighed the cost of facing the demon's flame versus the opportunity to damage it while it remains trapped in the black blob. Thankfully, the fire that erupts from the demon each time Kleve scratches or bites it, seems to have a reduced effect on the bodyguard. Still the demon's flame remains as strong as ever, and doesn't seem to be much diminished...

=================================================

Kaylyn is next
- Fire Aura: Take 6 fire damage at start of turn from the balor
- Rotting Presence: Make a DC 13 CON save or take 5+1 necrotic damage
- Roll a concentration check for Shadow of Moil

Sekkar is also next
- Rotting Presence: Make a DC 13 CON save or take 5+2 necrotic damage
- Fetid Cloud: Make a DC 11 CON save or be poisoned until the start of your next turn
- If you take damage, roll a concentration check for Hunter's Mark

Bulezau #1 is affected by Mind Spike, and will subtract 1d4 from it's next saving throw before the end of it's next turn

UPDATES:
Kleve advantage rolls: 10, 22, 26

MAP:

 Round 5 !!

DC 13 CON save: 12  DC 11 CON save: 7

The clouds of poison around Sekkar finally caught up with him. He felt sick. Still, he tried to attack.

(Disadvantage for poison)

BA Hunter's Mark moved on D4

Action1 : Attack: 21 Damage: 12 + 2 (HM)
Action2 : Attack: 15 Damage: 14 + 2 (HM)

if killed - rest on B5

Sekkar: Sorry, I didn't give you the whole information for the Fetid Cloud. I thought it might clog up the screen if I put the information there repeatedly, especially for such a low DC saving throw. But here's the full text:

A 10­-foot radius of disgusting green gas extends out from the dretch. The gas spreads around corners, and its area is lightly obscured. It lasts for 1 minute or until a strong wind disperses it. Any creature that starts its turn in that area must succeed on a DC 11 Constitution saving throw or be poisoned until the start of its next turn. While poisoned in this way, the target can take either an action or a bonus action on its turn, not both, and can't take reactions.

So is it okay if I just ignore the Hunter's Mark damage for these attacks? Unless you want a different choice of action or bonus action...

(OOC: Just a friendly reminder. The sunlight from Dawnbringer may free the Balor of the sticky situation that it has found itself in.)

Con save DC 13 13

Concentration vs fire damage 24

Concentration vs necrotic damage 12

The flames of the Balor once again burn her and Kaylyn realizes she needs to move back. Taking advantage of the restrained demon she climbs the ledge behind her (NW one square).  She then turns and fires of 3 bolts of eldritch power.

Attack: 30 Damage: 18

Attack: 24 Damage: 7

Attack: 27 Damage: 7

As a BA she then focus the her healing light on Rhayna for 6 hp.

 She targets the Balor with her attack. 

(Yes, remove the HM then!)

Dawnbringer sings exultantly in Sekkar's mind as his powerful scaly arms swing her blade back and forth at the demons, dropping both of them and sending them back to the Abyss. Kaylyn leaps up onto the ledge and fires three bolts of celestial energy at the balor, this time striking with all three, and the demon now begins to show signs of weakening.

Vizeran seems to notice this too, and having more experience with demons than anyone in the fight (except the demons themselves), he seizes the chance to end the conflict. Stepping back the the southern edge of the cavern, and climbing a ledge similar to Kaylyn's, the drow yells out over the howling wind two words: Take cover! Then, staring directly at the demon, the mage casts his most powerful spell. The noise in the cavern seems to disappear for a fraction of a second as the drow's soft voice echoes in every ear, speaking one simple word of power. It is spoken in the drow dialect of Elvish, but everyone understands...

DIE

Instantly the Balor explodes...

Everyone make a DC 20 Dexterity saving throw, taking 54 fire damage on a failed save, or half as much damage on a successful one.

(I think we got off lightly. Average d6 roll of 2.7)

DEX saves: Kleve 16, Bulezau1 9

The minotaur and the remaining demon are engulfed in the fire, and fall burnt to the ground, with the bulezau vanishing in a splash of ichor.

The modrons disintegrate into dust.

Kirin Dex Save: 18

Kirin is down now