The Tales of the Fellowship of the White Cloaks

Chill will absolutely use his reaction and Uncanny Dodge to take half damage.

Rhogar and Gorrah are up

"She's a squirrely one that one! But hold on a moment Krom & Kazri." Without missing a beat, Rhogar rushes into what he hoped was the best position to calling upon his own divine magic and creating an echo of it to send to cleric and paladin in kind, mending at least some of their wounds. He then holds his staff on high and from the Mythallar appeared to siphon just a sliver of the ambient magic whirling around it and into the staff, restoring some of its lost power. As for Gorrah, she zips over to the east to try and keep the frost maiden at least loosely within sight while maintain some cover of her own.

Movement(Rhogar): 20ft west, then 10 ft north.

Action(Rhogar): Use the Mythallar to regain all expended charges on his Staff of Power.

Bonus Action(Rhogar): Twinned(2sp) cast (2nd level)Hlal's Jest on Krom & Kazri, restoring 7 HP.

Movement(Gorrah): 60ft east, and if possible take cover behind the northeastern most stone pillar.

Action(Gorrah): Defensive Posture. 

Gorrah has moved as far as she can but can't reach another rock formation

Kazri and Oli are up and then back to the top of the order with Krom and Chill

Initiative: Round 5 - Krom (88/94), Chill (63/63)+2, Auril, Rhogar (76/87) Bless -6 & Gorrah (17/17), Kazri (72/104) Bless -6 & Oli (32/42) Bless -6

Oli will stay next to Rhogar. (If the Frostmaiden gets closer again to Rhogar, he will attack)

Kazri will dash to the rock where the Frostmaiden is hiding behind. (I don't believe she can get that with regular movement)

Kazri gets within 10 feet of the goddess who stands behind the rock formation.

As Kazri comes into view of Auril, the goddess teleports into melee range and reaches out and touches her with cold magic (to hit 28, 14 cold damage - 7 after resistance)

Kazri cannot take reactions until the start of her next turn.

Krom and then Chill are up

Initiative: Round 6 - Krom (88/94), Chill (63/63)+2, Auril, Rhogar (76/87) Bless -5 & Gorrah (17/17), Kazri (65/104) Bless -5 & Oli (32/42) Bless -5

Krom dashes around the Mythallar, trying to catch sight of the elusive goddess. As he moves, the dwarf clasps Moradin’s holy symbol and murmurs a brief prayer, dismissing the translucent maul and renewing his connection to the All-Father.

Action: Dash
Bonus action: Harness Divine Power to recover 1 2nd spell slot.
Movement: 50ft around the Mythallar as indicated in the spoiler below.
I'll dismiss the Spiritual weapon.

Chill will take a shot at Auril if he can where he is.  It looks like he has visual since she moved.  If needed he'll climb down to the 20 ft part of the rock. That really should be in line enough I think. He can climb to the 10 ft section also if needed.

He will use steady aim again

To hit 18, 35 damage 

Used piercer feat to reroll the 1d8 dice

Chill's vantage point 30 feet up does give him a clear shot at Auril. He lets the the bolt fly and it strikes Auril.

As the bolt hits her, Auril's body turns to slush and melts away. Auril instantly reappears on the other side of Kazri.  She is now a 10-foot-tall woman of fearsome aspect made entirely of ice and frost. Her eyes burn with a cold blue light, and a thin cloak of mist forms around her. Blades of ice grow out of her body at odd angles, breaking off before they get too long. When she moves, her body crackles.

She looks over at Chill and she creates a gem-sized ice crystal that hovers 5ft in the air in a space in front of her.  

"I shall make you mine" she speaks in a thunderous voice.

Chill must succeed on a DC 21 Charisma saving throw or become trapped in the crystal, which is immovable. If the saving throw succeeds, the crystal shatters and nothing else happens. A creature trapped in the crystal is stunned, has total cover against attacks and other effects outside the crystal, and takes 24 cold damage at the start of each of its turns. The creature can repeat the saving throw at the end of each of its turns, freeing itself on a success.

Rhogar and Gorrah are up

Initiative: Round 6 - Krom (88/94), Chill (63/63)+2, Auril, Rhogar (76/87) Bless -5 & Gorrah (17/17), Kazri (65/104) Bless -5 & Oli (32/42) Bless -5

Charisma saving throw is 17

Rhogar is blindsided for a moment as Gorrah's feelings of alarm and the crude image of Chill frozen in a block of ice floods into the dragonborn's mind. Still, as disorientating as it all was, he powered through and lurched forward into an unsteady jog around the Mythallar's western half, determined to see things with his own eyes. "No..... NOOOOOO!!" He cried out, and fearing the worst, leveled his staff as if intending to try and burn Chill free of his icy coffin.

But in catching sigh of Auril next, fear and the beginnings of grief turn to fury matched only in that moment by Gorrah's own. Together the two went on to coordinate in such a way that Gorrah's dive bomb's the goddess now more humanoid figure's face, distracting her just long enough for Rhogar to unleash a focused blast of divine power.

Movement(Gorrah): To immediate northwest of Auril, 5ft above the ground.

Action(Gorrah): Distract Auril for Rhogar.

Movement(Rhogar): 30 ft west of current position.

Action(Rhogar): Cast (1st level)Divine Breath at Auril.
(Spell, Lethal)Guiding Bolt - Attack #1: 13 Damage: 15 of radiant. (13,15)
Forgot to include bless: 4. 

Chill suddenly finds himself sucked into the gem that floats in front of Auril and is stunned, 

Gorrah swifty distracts Auril as Rhogar moves into range giving him just enough line of sight to get a visual on Auril. His blast of light hits her.

Kazri with Oli and then Krom are up

Initiative: Round 6 - Krom (88/94), Chill (63/63)+2 - stunned, Auril, Rhogar (76/87) Bless -5 & Gorrah (17/17), Kazri (65/104) Bless -5 & Oli (32/42) Bless -5

Kazri's heart tugs, as she sees Chill getting sucked into the gem. The ring around her neck starts to glow an dark amber radiant light. "Release him you monster!" She yell with true hate. She raises her sword high again and invokes Helm's aid. (Divine Smite lvl 3) The sword glows with a bright radiant light.

Attack1 (Advantage): 28 Damage: 9

Attack2: 19 Damage: 9

(If either attacks hits, it deals extra 20 radiant damage)

Oli meanwhile follows Rhogar guarding him.

Kazri's blade cuts at Auril as a blast of radiant energy accompanies the strikes.  Auril responds.  In ice morningstar appears in her hand but as she swings it at Kazri she is able to raise her shield and block the blow.

Krom is up

Initiative: Round 7 - Krom (88/94), Chill (63/63)+2 - stunned, Auril, Rhogar (76/87) Bless -4 & Gorrah (17/17), Kazri (65/104) Bless -4 & Oli (32/42) Bless -4

My next saving throw is 20 ... So close and yet so far.

“Release him at once!” Krom bellows as he strides towards the Frostmaiden. The dwarf thrusts a gauntleted hand towards the ice prison encasing the tabaxi and, uttering the command word, unleashes a spectral ram’s head at it, hoping to shatter the frozen cage.
At the same time, Krom chants a hymn of evocation, conjuring a large translucent maul behind Auril. An unseen force swings the weapon with crushing intent, bringing it down upon the goddess with divine might.

Movement: 25ft NW from my current position
Action: Ring of the Ram against the crystal cage trying to break it. I'll spend 3 charges. I'm posting the athletic check and the attack roll as I'm not sure which of those roll is the most suitable in this occasion, I'll leave the final decision to our DM. Athletic check 29 - Attack: 10 Damage: 25
Bonus action: Spiritual weapon at 4th level against Auril
Attack: 19 Damage: 7

Krom moves forward his dwarven anger rising as he bellows a command at Auril.  But she only laughs, and laughs even harder at his feeble attempt to break Chill out of the gem that holds him imprisoned.

The spectral ram's head slams into the gem that holds Chill trying to break him free but as the ram's head dissolves the gem remains where it is, as pristine as it looked a moment before.

The spiritual hammer that Krom has conjured then slams into Auril and her laughter turns to anger.

Chill, stunned and trapped, feels the cold of his prison but try as he might he cannot break free. (24 cold damage is halved due to resistance, 12 total.)

Auril breaks off an icicle from her body and it transforms into an Ice Mephit. 

She then swings her morningstar at Kazri who is able to parry and block the blows.

The Ice Mephit then claws at Gorrah but the pseudodragon is too quick and dodges out of the way.

Rhogar and Gorrah are up

Initiative: Round 6 - Krom (88/94), Chill (53/63) - stunned, Auril, Ice Mephit, Rhogar (76/87) Bless -5 & Gorrah (17/17), Kazri (65/104) Bless -5 & Oli (32/42) Bless -5

Gorrah smoothly transitioned from fluttering dodging the Mephits swing to feigned attack at the creature's eyes before zipping away off to the east. "If you will not relinquish your grip on him willing, then BURN!!" The dragonborn meanwhile declared, before with a flourish of the staff above his head, he brings it down flinging another explosive bead of fiery destruction! And with any luck, he dared hope it might even melt Chill's prison, if not weaken it enough to aid in the Tabaxi's escape.

Action(Gorrah): Disengage.

Movement(Gorrah): 40ft east of current position.

Movement(Rhogar): 30ft northwest of current position.

Action(Rhogar): Cast from Staff at (5th level)Fireball at Auril, Ice Mephit, & Chill(if applicable). Dex Save(DC 16) to take 28.

Gorrah zips out of range of the combat and a moment later a fireball explodes.  The ice mephit explodes in shattered ice as it is destroyed.  Auril moves enough to take half damage but the fire still burns her fiercely.

The crystal gem that imprisons Chill also melts away freeing him. 

Chill is no longer stunned and appears in an unoccupied space of his choice within 30 feet of the shattered crystal.

Auril swings her morningstar at Kazri again but misses.

Kazri and Oli are up

Initiative: Round 6 - Krom (88/94), Chill (53/63), Auril, Ice Mephit, Rhogar (76/87) Bless -5 & Gorrah (17/17), Kazri (65/104) Bless -5 & Oli (32/42) Bless -5

Chill will appear 30 feet west