The arena: Monster killers.

The mongrel bites and claws at Nadir but can’t get her with 2 17s. 
The second steeper bites at Count but can’t get him with a 14. Count and Yoku are up. 

Count will continue the Green-Flame Blade pattern going and strike at the steeper.

Attack: 24 Damage: 11

Temp hp: 9 or current 6

Sir Spitz will disengage and back up 15'

Sir Spitz temp hp: 9 or current 8

Yoku targets the last Male Steeder
(Bonus Action, move Hunter's Mark to the Male Steeder)

Yoku Attacks, Longbow, Hunter's Mark, Colossus Slayer: Attack: 23 Damage: 16 

That kills it! The guard once again chops at nadir, but it bounces off her armor once more with a 5. 
Nadir, you’re up. 

Nadir returns blows with the mongrel and the guard, with short and dagger, respectively

Attack: 12 Damage: 6

hex (if it still applies despite the Mite being gone): 2

Attack: 10 Damage: 3

hex (if it still applies despite the Mite being gone): 1

temp HP at max already.

I’ll say that the hex doesn’t. Those both hit! Roll the dead 8

The guard goes down with a save of9 but the mongrelfolj retaliates at Nadir, catching her with a claw for 5 damage. Count is up!

Count will swing the flail: 

Attack: 15 Damage: 4

Temp hp if higher than 7: 6

Yoku uses a bonus action to move Hunter's Mark to the Mongrelfolk

Yoku's Longbow, Hunter's Mark, Colossus Slayer Attack: 18 Damage: 11 

That kills it! 4

No rests for you. 6

As the last enemy goes down, several more appear, 30 ft away from the group. New order goes Nadir, Dolrik, Night blade, ox, another mud mephit, oblex spawn, count and yoku, oblex spawn, needle blight. Nadir is up!

Nadir throws a javelin spartan like  at the night blade

Attack: 10 Damage: 5

And does it again with an action surge,

Attack: 13 Damage: 4

then draws her short sword.

Darn, the Unlucky feat hard at work. 

So close…

Dolrik’s roll the dead: 1

Night blade goes down. The ox moves and dashes to reach you, the mud mephit moves and dashes as well.  So does the obleck spawn. Count and Yoku are up!

Yoku will move Hunter's Mark to the Mud Mephit and loose an arrow

Yoku Longbow, Hunter's Mark, Attack: 13 Damage: 9 

Count will cast Green-Flame Blade and swing at the ox (fire dame for the Mephit):

Attack: 18 Damage: 4

Temp hp maxed

(Bah, lost max damage and got that red bar)

4 fire damage to the Mephit.