Boona steps around the clumsy statues blows and moves up the stairs to the top platform ( staying within range) to take more swings at the goblin. ( pretty sure her moving to the top + her extra height + the maul keeps him in melee range.)

Attack: 18 Damage: 14

Attack: 22 Damage: 8

Fergus:

Continuing to play his harp, Fergus sends a pair of solid notes at Ruxithid, hoping to make contact and impair any invisibility-related shenanigans.  He then waltzes up to the massive statue and says to Boona, “You’ve got this!  Pound it to rubble or clobber the METH head!” as he kicks the statue in the shins.

Starry Wisp on Ruxithid:  Attack: 13 Damage: 13

(Move up to the statue, bonus to give Boona inspiration (1d8), which also triggers an attack Fergus can make.  Don’t forget your temporary hit points and heroic inspiration Fergus gave after the short rest!)

Dazzling Footwork attack on Statue:  Attack: 12 Damage: 6

Quinn runs for the western stairway leading up to the platform. He stows Lightbringer and grabs two darts from his belt. He flings both darts at the same time and both land, sinking into The Chosen One.

Move: 40ft up the western stairway

Bonus Action: cast Hunter's Mark on Ruxithid.

Attack 1: 24 to hit for 10 damage. Target is Vexed. Quinn has ADV on next attack roll against target.

Attack 2: 25 to hit for 6 damage. Target is Vexed. Quinn has ADV on next attack roll against target.

OOC: I used my last "Favored Enemy" Hunter's Mark which does not use up a spell slot. 

DM: Quinn has the Concentration Breaker feature from the Mage Slayer feat. If Ruxithid is concentrating, it has Disadvantage on the saving throw it makes to maintain Concentration.

(before his turn) Jurgen asks "Boona, you OK if I climb you to get to Ruxithid?"

Boona shrugs in the least bothered way possible.

Jorzu blasts at Ruxithid with balls of crackling energy, but fails to strike him.

Boona climbs the stairs, and circling the statue somewhat, slams Ruxithid with her maul. He shrieks in pain, but you notice that Boona's massive maul doesn't do the damage one might expect; it appears as though some of the force was somehow absorbed by the statue, which suddenly sports a few minor new chips transferred from Boona's slam. (Her second blow is successfully dodged by Ruxithid.)

Neither Fergus' musical mote, nor his fancy footwork, seem to affect either Ruxithid or the smiling statue.

Quinn runs partway up the stairs, flinging a pair of darts at the levitating goblin. Again Ruxithid shrieks as both projectiles hit him, but again it seems as if the statue somehow absorbs some of the impacts.

Jurgen prepares to scale Boona (it's 30' of movement to run up the stairs to Boona, and another 20' to climb her.)

Bryony may act. (I presume Jurgen dashing to reach and climb Boona?)

Jurgen will dash.

Ruxithid turns toward Boona (with Jurgen now standing atop her) and singing a high note, unleashes a flurry of crystalline psychic tendrils from his brain. Boona must succeed on a DC 15 Dexterity saving throw or take 6 psychic damage and have the stunned condition until the start of Ruxithid’s next turn.

He then draws his scimitar, and takes a pair of swings at Jurgen while continuing to levitate behind and above the smiling statue.

Psi-Charged Scimitar Attack #1 vs. Jurgen: 24. Hit: 16 slashing damage plus 7 psychic damage.
Psi-Charged Scimitar Attack #2 vs. Jurgen: 23. Hit: 11 slashing damage plus 5 psychic damage.

The statue just smiles.

Everyone may act. (Boona should make that Dex Save first.)

Jurgen uses his reaction to cast Shield and fwort Ruxithid. 

He then casts Green-Flame Blade and attacks. (28 to hit Ruxithid, with 13 slashing damage and 4 fire damage). Fire then leaps to the statue (for 9 points of damage).

Fergus:

(Boona, that inspiration can be used on the save if needed)

Fergus tries the harp song again, hoping to light up Ruxithid.  This time he says to Quinn, “Strike hard and fast!” and he attacks the statue once more himself with a roundhouse kick.

Starry Wisp at Ruxithid:  Attack: 24 Damage: 9

Bardic Inspiration (1d8) to Quinn.

Magic Unarmed attack at the statue:  Attack: 8 Damage: 5

Boona Dex Saving Throw- 20

Boona did not like whatever the crazy goblin had just tried to do to her and in response she swung hard at him.

Attack: 20 Damage: 14

Attack: 14 Damage: 10

Quinn grumbles and curses under his breath about not being able to get up close and engage Ruxithid. He stows his shield in exchange for his longbow. He runs up to the top of the steps, hoping to pull some focus from Ruxithid but maintain distance from the statue.

Attack 1: 17 to hit for 16 damage (7 + 5 colossus slayer + 4 hunter's mark)

Attack 2: NAT 1! 

DM: IF that 17 does not hit, I'd like to add the d8 from Fergus' bardic inspiration die.

Screaming and squealing, Ruxithid takes a flurry of hits, even as his smiling statue guardian seems to absorb half of it. (The stone guardian, meanwhile, seems to slowly be healing as well - the cracks mending in some sort of arcane regeneration process.) Ruxithid is bloodied; the statue not so much.

(Quinn: Fergus' bardic inspiration die unneeded. 17 just hits the statue.)

Jorzu and Bryony may act.

Jorzu 

"Hmmmph" groans Jirzu as his Force balls fly wide of their target. "How 'bout you stop moving!" He grabs a bead from his pouch and throws it at Ruxithid. Somehow it manages to fly all the way to its target as if propelled by magic and shatters above the goblins rock encrusted head, it showers Ruxithid in glittering red dust. As the dust settles it begins to harden like a crust around the goblin.

A - casts Hold Person with a DC15 WIS save or Ruxithid becomes paralysed. 

The red dust settles upon Ruxithid: DC15 WIS Save: 6

(Natural one!)

The dust freezes upon him for a moment in the air before dissolving into a horrid, brown dripping goo. He turns and scowls at Jorzu. (Legendary resistance; he chooses to succeed, instead.)

He stabs a finger at Jorzu, commanding his massive guardian, "Crush that one!"

He disengages and flies to the far west wall of lava, as his smiling statue lumbers forward.

(Boona, Jurgen, and Fergus may each have an opportunity attack on the statue as it lumbers by.)

Guardian Fist Attack #1 vs. Jorzu: 14. Hit: 12 bludgeoning damage.
Guardian Fist Attack #2 vs. Jorzu: 9. Hit: 11 bludgeoning damage.

Everyone may act!

Jurgen Opp Attack (15 to hit for 13 damage)

Fergus’ AOO:  Attack: 25 Damage: 8