Velon's crit gives him an attack with his bonus action per Great Weapon Master.  I believe Dai was adding crit damage himself so won't roll that.

Attack:  23 , Damage: 12 , Fire crystal: 1

 Cratol will continue killing the slaves at the door by him. ( He will use another Ki point to get in more attacks)

Attacks: 20, 26, 30, and 17

Damage: 13, 11, 10, and 12

Morgaine still goes after the Mindflayer that has Poljen in it's grasp, her fury evident in the attacks. 

Scimitar Attack : 27

Damage : 11

OOC: posting Morgaine's attack for her next turn

A number of projectiles streak up and strike at the levitating mindflayer, it crumples and falls back to the ground. The construct it had called forth wavers and fades even as Velon strikes a mighty blow.

Between the pair, Mari and Morgaine quickly tear apart the one trying to eat Poljen, ripping large wounds in its abdomen. It too falls.

Helped by a few arrows from Lia, Cratol finished off the last of the slaves by the northern gate even as Zz'Pzora does the same with those trying to attack the warriors near the brain.

Within a few moments, the only active enemy left here is the brain, for now sitting securely behind its walls of energy.

But that won't last for long, the banging at both gates intensify, and you can hear large numbers of people battering on them with weapons and spells. Gamliel reports that it could not discern much about the barrier.

Letting the Storm do its job at suppressing the brains actions, he sends another lightning bolt into its defenses. While he has the moment, Lawrance studies the barrier, wondering how he can bring it down without the typical Disintegrate 

Velon calls "let's hit that brain's, ah, shield wall thing, hard and try to get to it before they get to us!"  Perry and Mari both nod and get to work with spell and blade.

MARI
Main attack: 12   Damage: 9
Off hand attack: 29   Damage: 10
Sneak attack on either hit: 20

PERRY
*Activates Hexblade's Curse (including crit on 19 and 20)
Attack 1: 14  Damage: 9
Attack 2: 16  Damage: 15
Attack 3: 24  Damage: 15

VELON
*Quickens Haste and with GWM, and Smites on hits
Attack 1:  12 , Damage: 26 , Fire crystal: 6
Attack 2:  18 , Damage: 24 , Fire crystal: 6
Hasted Attack:  25 , Damage: 22 , Fire crystal: 3
Possible Smite on hit: 18
Possible Smite on hit: 9
Possible Smite on hit: 5

Adding to the assault on the brain and it's defenses, Lia whispers "Swift death to you who have wronged me" and sends an empowered arrow into the brain's shield. "Is this going to do any good? " She asks, also sending more healing to Poljen after he was released from the flayer. 

Lawrance replies back "This isn't a normal Wall such as the ones I create. It's a lot larger, so maybe we don't need that particular Disintegrate spell to take it down?"

 Poljen thanks Lia for the healing.  "I will recover.  My thanks to you, Mari and Morgaine.  Now, is there any way I can get through that magic wall to attack the brain creature?"

Cratol shifts to the barrier around the brain bashing at the shield with his staff in hopes of breaking through. 

Attacks: 20, 24, 29, 20

Damage: 15, 9, 9, 10

Most of the group descends on the elder brain and its protective barrier, battering at it. Its easy enough to hit, but seems to absorb your blows. The shimmering wall does hum louder, then begins to crack. It shatters when Morgaine gets in a good hit, and then Zz'Pzora tears past, digging her claws into the soft flesh of your enemy.

As soon as the barrier goes down, Lawrance rummages through his pouch, finding a small pouch of dust. Moving quickly, he heads up towards the brain's vat, sustaining the storm and lightning attacks.  

Poljen continues swinging his massive axe, trying his best to chop through the barrier and destroying the soft matter of the brain.

Attack 1 w/Adv 18  19

Attack 2 w/Adv 27  11

Damage 1 & 2 12  14 

Cold Damage 1 & 2 2  6 

As the barrier goes down Cratol will attack the elder brain with his staff hoping to end this fight quickly.

Attacks: 22, 15, 14, 23

Damage: 15, 13, 13, 9

The group continues its attack after the barrier falls, striking at the brain on all sides. It isn't long before it retaliates however. It briefly pulses with a blue light, and psychic energy washes over those nearby.

(Rolling save first, then posting) 18 INT save

 The wave of energy rolls over Lawrance, hand outstretched to drop some of the powder into the water and he just...stops, the ravaging mental energy roiling through him. His conjured storm fades away as he loses control over it from the pain. 

Poljen once again feels a wave of energy blast into his head, and braces to shake it off.  INT Save w/Adv  13  5 

He slowly stops swinging his axe as the pain lances through his mind.  29

Cratols saving throw with advantage: 14, 7

Cratol stops attacking as he is stunned.

Damage: 23

Velon INT Save: 20 
Damage: 21 

Perry INT Save: 10 
Damage: 19 

Mari INT Save: 26 
Damage: 22 

Shocked at the sudden disablement of all her friends, Lia moves forward just enough to cast Banishment on the brain in the pool. (About 20'?) "By Sune's irresistible light, begone, aberration!"

(ooc- DC17 CHA)

As the warriors of the silver blaze stagger under the onslaught of the evil cerebral mass, Lia attempts to cast it out of this world. Its form wavers briefly, but soon reaffirms itself. A large tentacle reaches out to grab Mari and fling her away from the pool, the young half elf bouncing along the floor as she rolls to a stop.

The beating at the doors continues