As his rage diminishes and the funny warm feeling makes a bunch of his bruises go away, Wripers starts gnawing on the Divine Master's leg, like a hound to a ham hock. 

[OoC: At this point, his intelligence is pretty much on par with a dog, or a dumber one at least, so don't be surprised if some of his non-combat behaviors reflect that. Except leg humping. Something tells me that's too far for this campaign.]

Something tells me you are right, Bold. 

Now that it seems everyone is ready, Does Amari drop concentration?

"Let us take a few moments to prepare for the Primal Master's return," Ruin says, hefting his axe and taking a position right behind where the Primal Master disappeared from. "Wrippers, our final enemy shall soon return. The instant he does, throw him to the ground to make him easy to destroy."

Ruin will go ahead and drop Fizban's in favor of Spirit Shroud to get a bonus d8 of radiant damage on his attacks. He will ready his action to strike the Primal Master twice with his greateaxe the instant that Wrippers throws him to the ground.

The metal man says things Wripers doesn't quite understand. So he goes to rip the Arcane Master's head off. 

Why? Your guess is as good as mine. 

[Athletics: 18]

Umm...ok.

Wripers rips (see what I did there?) the head of the Arcane Master off, and now has its head.

Kass watches the savage little kobold rip the meatsack off, the facial features swimming around due to a lack of supportive bone, and his stomach begins to rebel.  Dry heaving just a little bit, he stubs out his smoke and draws his vorpal scimitar and his rapier, readying himself for the Primal Master's return.  

"I should have remembered that our  companion has a malfunctioning processor..." Ruin says matter-of-factly. "I suppose it matters little... one way or another the final enemy shall fall."

It seems Man_of_Dust has disappeared for a little bit. No problem, we shall continue

Amari drops concentration, and the Primal Master pops back into existence, dazed and confused.

Amelia > Kass > Ruin > Wripers > Evelyn > Primal Master. (since Amari is gone, I didn't include her in this order, but if Man_of_Dust shows back up, feel free to throw in a turn)

Amelia, GO!

Amari does indeed reliquish concentration on her banishment, and immediately greets the reappearing Primal Master with a blast of radiance.

• Guiding Bolt spell attack (at 6th-level): 36 to hit, causing 64 radiant damage

With a mighty sweep, Amari blasts forward the power of the gods, which slams into the primal master with a mighty flash for a CRITICAL HIT!

Amelia, then Kass, then Ruin

Amelia, GO!

Kass sees the Primal Master outlined in a glittery glow, and shouts quickly to Amelia.  "Let me try to end this now!"  

He then leaps forward with his vorpal scimitar, hoping to sever the Primal Master's head in one quick snicker-snack, throwing in a Defensive Flourish and an offhand attack for good measure.

Attack 1: 22 Damage: Unable to parse dice roll. 
Attack 2: Attack: 31 Damage: 10
Defensive Flourish bonus: 3 damage added to one attack that hits (the number rolled is also added to my AC for the turn)

Offhand attack: Attack: 13 Damage: 11

Celestial's attacks:
Attack 1: Attack: 20 Damage: 14 plus 2 hp for Amari
Attack 2: Attack: 16 Damage: 17 plus 2 hp for Ruin

Sadly, only one of Kasses attacks land, the others bouncing of the rough hide of the Primal Master, which is now covered in dripping acid and poison. Both of the Celestial's attacks strike true, smacking the Primal Master with a double "thunk!"

Ruin, then Wripers, then Evelyn

Ruin, GO!

Ruin will attack the Primal Master with his greataxe... on his first attack he will Eldritch Smite as well, knocking the PM prone to get advantage on his next attack.

Greataxe 1: Attack - 25; Damage - 13 (magical slashing) + 7 (radiant, from spirit shroud) + 19 (force) = 39 damage
Greataxe 2: Attack - 34; Damage - 20 (magical slashing) + 7 (radiant) = 27 damage

With his bonus action, Ruin will cast a quickened booming blade

Booming Blade: Attack - 31; Damage - 14 (magical slashing) + 3 (radiant) + 17 (thunder) = 34 damage. In addition, if the PM willingly moves 5 feet or more before the start of Ruin's next turn, he takes an additional 20 thunder damage (standing up from prone requires half a character's movement speed... so standing up should trigger the bonus Booming Blade damage).

Edit: also, prone creatures have disadvantage on attack rolls.

Ruin leaps forward with the power and strength his creators designed him for, a weapon of destruction. His three mighty, magic-infused strikes slam into the Primal Master, cleaving through flesh and bone like a knife through butter. The Primal Master is now prone!

Wripers, then Evelyn

Wripers, GO! (remember: because the Primal Master is prone, you have advantage on attack roles against it)

The little guy had planned on throwing his newly procured head, but with the brute now lying on the ground, he's forgotten why. Moving in, he drops it with a loud, wet slap. 

[I assume that counts as an action]

He then takes up his hammer and swings in a hard arc. 

[To hit: non-nat 20, Damage: 14]

His stomach growls. He's hungry. 

Dropping the head would be his free item interaction, so he gets to take a full turn. Besides, I don't really care about that stuff, it bogs down the game for no reason. So Wripers can take full turn if he wants.

Quote from Raccoon_Master >>

Dropping the head would be his free item interaction, so he gets to take a full turn. Besides, I don't really care about that stuff, it bogs down the game for no reason. So Wripers can take full turn if he wants.

 [Mmmmm... nah, I could go again, but let's keep it rolling with whoever's next.]

Evelyn, time to shine!

Ok, gonna bot for Evelyn since she said she would continue with the "Bones to Jelly" ability each turn

Attack roll: 23

CON Save: 30

Evelyn reaches for the Primal Master, curling her ghastly hand around its ankle. The Primal Master shakes her off, sending her flying back.

Primal Master's Turn!

The Primal Master roars, and their form becomes that of slithering acid and steaming poison. With a mighty crash, they swing both of their clawed fists in a downward arc, smashing into the party.

Claw attack VS. Wripers: 23 to hit, 43 Slashing plus 9 Acid

Claw attack VS. Ruin: 15 to hit, 27 Slashing plus 9 Acid

Amelia, then Amari, then Ruin

Amelia, GO!