Fran would pivot to face the new foe as it charged into battle. She’d reach for her trusty wad of grease and move in just close enough to lob it right beneath the beast, hoping for it to fall prone in time for the melee attacks. Brutus would nip at its heels.

Casting: Grease Dex DC 16 

Bonus action: 9 Damage: 6 

Tyr Almighty, that's one big gnoll, thinks Ordrag as a feeling comes over him like he has just swallowed a rock. But no-one ever accused him of running from battle, and he wasn't about to start now. With an even louder yell than before, Ordrag turns and meets the demon's charge head-on...

Action: Attack/Longsword.
Attack#1: 16 Damage: 9 slashing.
Attack#2: 17 Damage: 9 slashing.
Attack#3: 18 Damage: 9 slashing.

Bonus Action: TWF/Warhammer.
Attack: 23 Damage: 13 bludgeoning.

Savage reroll for Longsword #3: 12 slashing.

Adray will rush up to the creature in a flanking position with Ordrag.  He'll strike out at pressure points hoping to stall the creature out.

Attack: 10 Damage: Unable to parse dice roll.

If it hits DC 15 con save or be stunned

Attack: 23 Damage: 6

If with advantage 23

Bonus Attack: 24 Damage: 7

If with advantage 13

There was something to it - to Choir's attempt to wake up Lulu (if it was indeed her dream). The new opponent looked quite menacing. ( Save: 30)

Whether because of his weight or the (un)natural dexterity, but the demon did not fell down. He did noticed Brutus's attack, though, and huge flail in his hand raised and fall on the  back of the constract.

Flail vs Brutus: Attack: 27 Damage: 15 breaking the loyal companion to pieces.

Ordrag fared better in his attacks than poor Brutus and landed some hits on that enormous target, inevitably attracting its attention. An immediate swing of the flail answered warrior's barrage of steel.

Flail vs Ordrag: Attack: 36 Damage: 24

Adray used that moment to sneak behind the demon, but had to get through too much obstacles to get all the way through. Still, some of his attacks hit and he felt felt rock-hard demon's hide under his fist.

In fact, the hide was so thick (or so magical?) the gnombies, that obediently surrounded their former great leader, did not leave any visible scratches on it. 

But Polly's bolts did not miss. Almost. Placing warlock on the demon's list of targets. And now it was his turn!

A transparent flail appeared near Polly: Attack: 29 Damage: 18

while the real flail tried to reach Adray: Attack: 18 Damage: 16

                                                                     Attack: 22 Damage: 17

hitting again Ordrag on the way back: Attack: 33 Damage: 10

 Adray: DC 17 Constitution saving throw or be paralyzed until the start of demon’s next turn

Ordrag: DC 17 Wisdom saving throw or be affected by the confusion spell until the start of demon’s next turn

Then demon finally noticed Mooncolor. Not bothering with the lesser enemies, he charged over zombies toward the unicorn (if Adray and Ordrag are still active - they get AoO)

Choir!

WIS save: 17   (ha! made it)

By the gods, that demon packs a punch, thinks Ordrag. The first blow was bad enough, leaving a sizeable dent in his armor, but the second... it was enough to almost knock the half-orc senseless, and Ordrag is sure he felt a few bones crack. But there was nothing else for it but to grit his teeth and keep fighting.

It doesn't look like the big guy has left Ordrag's melee range, but if he did then here's the AoO.

Attack: 26 Damage: 13 slashing.

Choir skirts around Mooncolor, trying not to get in reach of the gnoll demon, and gets close enough to Ordrag to cast Cure Wounds for 33.

(Nice roll. Doubled my hit points)

Adray took the heavy blows and they knocked the wind out of him.

con save 10

 All he could do is stand there gasping for breath and unable to move.  He watched on as the hulking beast moved away to resume attacking his allies.

Brutus does not shatter into pieces. 

(Pulled from Artificer page. So, if I’m not mistaken Brutus would have approx 50hp+ pool)

STEEL DEFENDER

Medium construct

Armor Class 15 (natural armor)

Hit Points 2 + your Intelligence modifier + five times your artificer level (the defender has a number of Hit Dice [d8s] equal to your artificer level)

Speed 40 ft.

(Then just a question about grease. It’s an aoe I place beneath him. I see he Cleary made his save for me to have thrown it under him for my turn. But wouldnt he technically still start his turn in it and should make a save to move out of it?)

((Yikes! My bad, very sorry! Indeed - 61 HP (6+55, or you can roll and it will be 6+ 11d8. Was it so difficult for them to include companions in CS?). Also was reminded about existence of Arcane Jolt. Plus, right now Brutus also has a chance for an Opportunity Attack))

((And Ordrag is right about  AoO with correct shape demon did not leave his reach - and may be for the best))

Stomping through the zombies, the demon made a long laughing howl and attacked the Unicorn before the celestial could even react: Attack: 24 Damage: 17

(Save: 19 )

The sharp slapping blow was so strong, that Mooncolor was pushed away and despite all his attempts, fell to the ground. He stood up, though, made a step father back and  then charged at the demon:

Attack: 22 Damage: 10

Attack: 8 Damage: 6 + 12

He could as well attack a mountain - the gnoll lord did not move an inch.

Round 2

Fran Brutus Ordrag Adray, Polly!

The demon towers over all, making it hard to attack the vital body parts Ordrag is used to aiming for, but then he isn't sure if demons even have organs...

Action: Attack/Longsword.
Attack#1: 12 Damage: 7 slashing.
Attack#2: 14 Damage: 11 slashing.
Attack#3: 24 Damage: 11 slashing.

Bonus Action: TWF/Warhammer.
Attack: 26 Damage: 10 bludgeoning. Savage reroll: 13 bludgeoning

Having finally recovered, Adray rushes in.  "Keep the pressure on him," he shouts out and then tries again to stun the creature.

Attack: 25 Damage: 10

If it hits stunning strike dc 15 con or its stun until the end of Adray's next turn

Attack 2: 18 Damage: 10

Advantage if it was stunned 21  if that first strike didn't stun, try again.

Flurry for 2 bonus attacks

Bonus Attack 1: 29 Damage: 14

Advantage if it was stunned 14 again if 2nd try didn't stun he will spend another point to try if it hit

Bonus 

Attack 2: 27 Damage: 10

Advantage if it was stunned 15

     Polly mutters her most newly learned magical incantation and cats Tasha's Otherworldly Guise (bonus action) gaining immunity to fire, poison and the poisoned condition, devilish spectral wings sprout over her normal wings, and she flies backward, away from the demon, putting 40 more feet between her and it.  The casting of the spell makes her lose concentration on her Gnombies and they fall to the ground, once more inanimate...

     While flying back, Polly quickly says more common magics and sends six bolts of Eldritch Blast at the demon.  ((Prior BA spells allows second attack when action is an attack...))

EBlast 1.1 Attack: 25 Damage: 13

EBlast 1.2 Attack: 21 Damage: 13

EBlast 1.3 Attack: 27 Damage: 5

EBlast 2.1 Attack: 27 Damage: 6

EBlast 2.2 Attack: 9 Damage: 13

EBlast 2.3 Attack: 21 Damage: 13

(I did/do have Brutus in my extras tab. I updated his HP at lvl 9 I think. I will update to the 61HP now that shes lvl 11. And yes I've been excited to finally try arcane jolt. Fran's still got some tricks.)

The steel defender didn't go without taking a good dent to his armour though. Like the loyal companion he was from the core, Brutus wouldn't let the gnoll get away from his reach without nipping at his heals. This time there was jolt that came with his bite.

Brutus AoO: 12 Damage: 7
If hit, Arcane Jolt: 6 force damage

Fran would let out a string of whistles, praising Brutus to keep pressing the gnoll. He'd follow Adray and Ordrag in, positioning himself where he could deflect attacks!
(DA on attacks against party members.)

Loading her crossbow bolts, Fran heavily contemplated her next moves. She tried calculating what would have the most impact, but the truth was, there was no time for that. She'd take aim at the gnoll and fire her pair of bolts.

Attack 1: 20 Damage: 13 
Attack 2: 11 Damage: 7 

Not confident in her shots, she whistles for Brutus to take a bite once again.

BA: 15 Damage: 9

((Have to look in the notes more often, but I mean I wish they made a special table in the CS for companions/familiars/mounts etc. Right now you can not even properly add them in combat log!))

((Also, sorry, Adray is still paralyzed (what's wrong with me today?) and may be for the best))

This time Brutus did bit a small chunk of demonic flesh. It did not stop or slow down the monster but annoying construct was noticed once again. So was Ordrag, that again reached the demon with his blade and hammer, and, of course, Polly's bolts of energy (most of them). The response to Ordrag's blades was fast and quite furious: the demon did not bother with the flail - it was a whirlwind of teeth, a hurricane, that seemed to be in several places simultaneously:

vs Brutus: Attack: 29 Damage: 15

vs Ordrag: Attack: 18 Damage: 16

vs Choir: Attack: 27 Damage: 17

vs Mooncolor: Attack: 20 Damage: 14

When Polly sent her magic toward the monster, it stopped his assault and glanced in the direction of warlock.The transparent flail followed Polly and, despite being quite far now, attacked again: 

vs Polly: Attack: 34 Damage: 30

Now he was using his flail again! And it hurt:

vs Brutus: Attack: 28 Damage: 17

vs Ordrag: Attack: 28 Damage: 16

vs Mooncolor: Attack: 35 Damage: 11

Brutus: DC 17 Constitution saving throw or be paralyzed until the start of demon’s next turn

Mooncolor : +16 damage

It was that moment when everyone (probably with exception of the demon) felt deep sorrow and fear of loss of something dear. The feeling was coming from outside, inflicted upon you like a weeping cry you can not stop. The feeling passed, leaving just a memory of it. The demon (it looked like he did senses something) gave out another mad cackle and looked up.

Choir!

((What is this CS we talk of?))

     Polly falters and flutters for a moment taking the hard hit from it's transparent weapon, curses, but continues flying...

     And I'm assuming OwImp could have made his way back to Polly by start of Polly's next turn.  Not that he's likely to do much other than hide behind her...

((Character Sheet. And, yes, OwImp could return, of course, but might prefer to keep away - turned out, by pure RAW Spiritual Weapon do not have to be within 60ft of the caster after it was summoned))

(How badly wounded does the demon look?)

 When the demon bit her, Choir released a small burst of thunder, doing 10 damage to the gnoll god. (Wrath of the Storm, Dex save DC17 for half damage.)

Rapidly running out of powerful spell slots, Choir decides that keeping Ordrag (and if possible Mooncolor) alive will do far more damage to the monster than she could herself. Choir casts [spell]Cure Wounds on Ordrag again, for 19.

The first attack left deep tearing gashes in Brutus' armour. It was when the gnoll lashed out with his flail once again that caused devastating blow to the defender. Brutus tried with all his might to remain standing, but slowly his joints began to buckle in and he'd slump in a lifeless pile.

 Lulu...