The arena: Monster killers.

It doesn’t move but instead uses its breath weapon. Nadir and her horse need to make dc11 Dex saves or take 16 acid damage, half on success. 

You’re up!

Yoku concentrates on Hunter's Mark and uses a bonus action to move it to the black dragon wyrmling, then attacks twice,

Yoku Attack 1 (1d4+1d20+10) 2+19+10=31, Damage 1 (2d8+1d6+7) 7+4+1+7=Unable to parse dice roll.
Yoku Attack 2 (1d4+1d20+10) 1+6+10=17, Damage 2 (2d8+1d6+7) 1+1+5+7=Unable to parse dice roll.

Ben will also attack the wyrm, magic flare (1d4+1d20+3) 3+1+3=14, damage (1d12+1) 1+1=Unable to parse dice roll.

Yoku's temps 11/6, quivers (36/40)
Ben's temps 10/6

Dolrik re-ups the Channel Divinity through his Amulet of the Devout.

Rawrer distracts.

Maxed at 11 temp hp for both Dolrik and Rawrer.

For now count will keep the dancing sword where it's at and stay close to the group as well. 

[spel]Fire Bolt[/spell] at the dragon

Attack: 4 plus 16 Damage: 7

Temp hp: 6

Sir Spitz temp hp: 7

Plus 1 to the temp hp (did +4by mistake)

Fire Bolt was the spell

Nadir: 3 plus 12
Horse: 12

She tries to avoid the stream of acid emanating from the dragon’s mouth, then she whacks at it again twice.

4 plus Attack: 27 Damage: 11
3 plus Attack: 15 Damage: 8

temp HP: 8 and 6

Ooh nice. Those attacks take it down with no trouble! 
7 (3-8 is another wave) 4

The dice hate me. 

An animated ballista appears on the other end of the bridge! Count’s side, that is. 50 ft from the group, 100 from nadir. The three of you who haven’t gone this round, go ahead and go. 

(Which of us can go? I think we all posted an action that turn.)

(Oh whoops. I only saw Nadir’s. Don’t know how I missed that)

It rolled lower than you on initiative so all of you can go. 

Going before or after the ballista,, Yoku uses a bonus to move Hunter's Mark, then readies his full Action to use Extra attack after Ben's turn.

Ben will spend a second scrolls of magic missile, 4+1+1+1+1+1=17

Yoku then releases two arrows, the first hit will use Colossus Slayer for an extra (1d8) 1 damage

Yoku Attack 1 (1d4+1d20+10) 4+9+10=Unable to parse dice roll. Damage 1 (1d8+1d6+7) 4+3+7=14

Yoku Attack 2 (1d4+1d20+10) 4+16+10=30, Damage 2 (1d8+1d6+7) 7+6+7=20

Yoku temps 11/11, quivers 34/40

Ben temps 11/11

That injures it badly. Several parts are damaged.

Count will move 20' closer and cast Fire Bolt

Attack: 2 plus 11 Damage: 19

BA : send sword to the ballistic and attack

Attack: 3 plus 18 Damage: 11

Temp hp max

Skr Spitz temp hp 9 or 6

That's a lot of red rolls...

Nadir moves back to the group and sheathes her trusty stick. Back with her companions she Create Bonfire. DEX DC 15 or 7 Fire damage.

temp HP: 7 and 6

Quote from cyreon >>

Nadir moves back to the group and sheathes her trusty stick. Back with her companions she Create Bonfire. DEX DC 15 or 8 Fire damage.

temp HP: 11 and 10

 She creates the bonfire at the ballista’s position, in case that wasn’t clear ;)

Toll the Dead at the animated weapon, hoping the tolling will hasten its decomposition.

DC 16 Wis Save or 8 necrotic damage.

Rawrer distracts. 

Maxed at 11 temp hp for both Dolrik and Rawrer.

The sword hits, and the Combination of spells finishes its destruction. 4-8 is another wave. 2 and 4