Feeling comfortable with where he is right now, Onyx won‘t move but take a deep breath instead (recover Feline Agility) and shoot two divine arrows (3 left) at the Firebolg:

• Attack: 20 Damage: 15
• Attack: 29 Damage: 12
• Goading attack on the first hit: +5 damage and DC 16 wisdom save or disadvantage on all attacks except against Onyx (1 left)

Salys dismounts and gestures sharply at the scythe, causing it to begin to glow red hot. Then sends Bearskr forward to grab the scythe and move away if it drops it, or attack if it doesn’t.

Salys: Heat Metal 9 fire damage and a dc 16 con save or drop the scythe.

(If it doesn’t drop the scythe, use the attack below, if it drops it, pick it up as an object interaction then disengage and retreat as much as possible.)

Bearskr: Attack: 21 Damage: 10

(Rolled for it, but forgot to mention Bearskr will attempt to flank if it attacks.)

Con Save: 25 He continues holding scythe.

((holding a Heated object gives it disadvantage on attacks))

Robin again casts tasha's mind whip this time at 2nd level, just targetting the main enemy...

DC 18 Int save for half damage and no other affects, otherwise take 13 damage and suffer other effects.

Again, will use chrono shift if they make the save.

Wis Save for Goading Attack: 18

int Save for Mind Whip: 23

Chrono Shift: 6

The Firblog growls as he barrage of attacks strikes him and many conidition restrict. His head snapping to  side as he starts speaking in Deep Speech almost to himself as the green fiery aura around him flares up with each attack.

For Deep Speech Speakers:

[Legendary Action]

The man turns his head as he looks around at everyone as he starts to sing what sounds like a sea shanty as he draws his firearm and points it above his head, the scythe seem to return a blacken color expect for the heated parts, "The wind it blows from the east nor'east. Our ship will scud ten knots at least. The purser would our wants supply. So while with life we'll never say DIE,"
He fires a glowing green shot into the ceiling that rips through the ceiling two stories above.

"Take your prize but do be wary, I shall bring my own crew next time," He states to Onyx, pointing above where he can just make out the Lantern hanging high on the ceiling covered in a cloth.

The air rumbles as in distance, cannon fire sound off followed by whistling sounds closes in on the group before the walls around the room shatters as spectral cannonballs starts besieging the site from outside, showering the building in explosions and the party starts falling as floor gives way and the building starts upon them before the floor collapse under them as the debris proves to be too much for the old floor to take.

Dex DC 17 to avoid the cannonballs
Damage: 4  Bludgeoning (Half damage from successful save)

Dex DC 15 to avoid the worst of the building collapse
Damage: 13 (Half damage from successful save)

After a few seconds, everything starts to settle but most of the building is resting around them. Everyone hearing shouting of many people before a single roar and movement everyone feels through the debris follows then heavy dragging footsteps just out of sight followed. Muffed shouts can be heard through 

"Hey! Are you ok? You shouldn't moving! Stop! Stop!"

"There more underneath. Your concern should lay with them," The scythe's muffed voice cuts through. the party hears scrambling of footsteps as debris starts being shifted around.

"Hey! Come here! A orange isn't going to fix you up! Where are you going? Gods dammit! Come back! . . . . Let him go! We have reports those guys with the wall house were seen in here! We need to dig them out!" 

 Athletics DC 15 if you wish to try to push your way out. Any other escape plans are acceptable as well. Note, no one can see anything much lights coming through cracks and holes from Search and Rescue.

Resfaen Dex Save #1: 16

Resfaen Dex Save #2: 10

Athletics: 17

(Forgot to mention the use of 'Lucky' if they managed the save, but likely too late for that now.)

Robin dex save 1: 12
Dex save 2: 5

She casts dimension door to teleport herself free of the rubble.

Resfaen takes a moment  as she managed to evade the worst of the attack and following collapse but still finds herself buried, She takes a few deep breathes before attempt to force herself through the wreckage but finds it too heavy.

Robin is assaulted by the cannonballs before she can recover from the cannonball, the debris slams into her as she falls down. Getting her bearings, she cast her teleportation spell out of the rubble. Looking around she finds a dozen or so guards, holding torches and lanterns, digging through the rubble, one guard, probably the captain or similar spots Robin, "Hey! Are you ok? are there more with you? Are they in the ruins?"

"Yes, there are more in there." Robin confirms. She starts aiding them in digging the others out. She looks rough, her red braid loose now, long red hair covered in dust and dirt, her cloak torn in several places, and a large bruise forming on the side of her face. Blood flows from a bloody lip, and she favors her arm as she works to dig.

Dex1: 26

Dex2: 15

Acrobatics: 9

Athletics:21

Reroll Acrobatic with my temporary Luck point (forgot the name of the spell, but should still be within the hour): 11

Onyx easily dodges the impact of whatever hit the building and as the walls start to crumble, he tries to get closer to the lantern. He tries to quickly jump and climb up the wall, but he slips and falls with the rest of the floor. He manages to avoid most of the falling debris and starts to dig himself out of the rubble once the  building stoped collapsing.

Onyx easily dodges the impacts, but even as the building is struck by the bombardment, he tries to climb and jump up the walls to reach the lantern, but he looses his grip and falls together with the rest of the floor. Once the building stoped collapsing, he starts to free himself as best as he can.

The first thing he does when he get‘s out, is to look and search for the lantern.

Salys dex save 1 13 2 22

Bearskr dex save 1 9 2 20

Salys con save for concentration 1 19 2 21 Maintains concentration on heat metal.

Athletics to get out: Salys helping Bearskr 22

Dodging the worst of the barrage and collapse, Salys and Bearskr push their way out and Salys mounts Bearskr to try and continue pursuit of their enemy, focusing on his spell to continue causing damage to him to try and force him to drop the scythe. Looking at the rescuers, “Where did that foul murderer go? He’s the one who attacked our residence and murdered people the other day!”

Heat Metal 6

Dex save to avoid the cannonballs : 5
Dex save to avoid the worst of the building collapse : 5

Con save to keep concentrating on bless: 16

Con save to keep concentrating on bless: 12

Athletics: 2 

"We didn't see any goliaths, Just that firblog fellow. Gave him a few pats to make sure it wasn't an illusion and let him do whatever since he refuses treatment after he ate an orange," The captain replies before giving more orders to focus the search as people emerge from the wreckage. Onyx searching the wreckage for the lantern and finds it after a few minutes, he misses it a few times due to the small cloak wrapped around it. in the mean time, Resfaen and Rogi are dug out by the rescues and other party members.

"Well that was unexpected." Resfaen says as she dusts herself off. "Anyone know which direction that firbolg went?" As she looks around and uses her Divine Sense ability to see if she can determine which direction it went.

Salys shakes his head angrily, “The goliath was the disguise, the firbolg is the murderer! Which way did he go?” 

He will continue to focus on his spell, causing the scythe to burn its wielder. (Looks like range is just to cast, after that as long as I maintain concentration, I can keep bonus action burning him.) 7

As she digs the others out Robin calls her owl to launch to the sky, seeking out the fleeing enemy...

Owl perception: 19

(for 1 minute total or 6 more instances of Heat metal but should be note, can only do it every 6s)

"Slow down! Explain yourself," The captain states as Resfaen and Rogi are found in the debris, this does take some time to clear the debris. After a clearer explanation, the captain looks around confused as he search the scene before pointing a direction, "He went that way ish?"

The owl searches from above but finds all manners of people running around, many guards coming towards the building but some still moving around searching but nothing standing out as big.