Hearing the warning from Aisha, Kasbis does not get any closer to this slab and does not cast identify.  “Begin your ceremony, we can protect you.  Duncan, get ready.”  Kasbis readies himself in case more demons appear.  

The ritual will take 1 minute to complete. Which is 10 rounds. As the first word is uttered for the prayer, there are demonic wails from from the stone slab as if in pain. Bursting from the slab is the monster with rows of teeth. There is a brilliant white 20ft chain tethered to the monster keeping it from going far. The prayer is keeping the monster tethered to its prison. In Abyssal it says "I shall not be denied my freedom! Each of you shall nourish me for days."

It is a large size monster with 10ft reach.

For this fight to make it much easier I am going with Side Initiative where 1 side goes then the other.

Monster - 15

Party - 1

Round 1

Zarkar the Marauder attacks Duncan 2x

Claw - Attack: 20 Damage: 7

Bite - Attack: 18 Damage: 13

Poison Damage 5

If Bitten Roll Con Save DC 14 on fail you are poisoned. You can re-roll each round to shake off the poison.

Now its the party's turn.

Aisha will focus on the ritual prayer calling on the power of Elestine to bind this evil.

((Not being at full health, and with 1/3 of our party busy on a spell… this is gonna be tough…))

Duncan instinctively tightens his grip on his glaive as the creature appears and approaches him. Taking a swing as soon as it enters his range, he then follows up with a series of quick blows, surging to do as much damage as possible, and finally concentrating to heal up just a bit.

reaction
Attack: 7 Damage: 4
action
Attack: 15 Damage: 9
Attack: 12 Damage: 6
action surge
Attack: 20 Damage: 12
Attack: 23 Damage: 8
bonus action heal 14

((OOC : Don’t wish to hold this up, please tell me if this is acceptable, or if Kasbis or Aisha would feel this is disruptive at all to what Aisha is trying to do.  Taking a risk here.))

Kasbis sees the very real threat this demon represents, he worries that it will be able to disrupt Aisha’s spell.  “Keep your focus Aisha, keep concentrating!  I’ll try to distract it, and make it harder to hit us!  You keep concentrating on the front of that circle!!”  

Kasbis casts darkness, focusing on the portion that the creature occupies and behind him, wanting to keep him in magical darkness and make it harder for it to connect with its attacks.  “Sorry Duncan, go by sound, focus on protection of Aisha!”  

Round 2

Duncan you notice your hits do less damage than expected as each cut only does half damage.

Zarkar growls as its blinded by darkness. It then unleashes Roar of the Fallen - 20 ft cone

Everyone Roll Wis Save DC 14  Half Damage on success

Necrotic damage - 16

Now its the party's turn

Kasbis wisdom save : 21

Kasbis shoots two bolts of force energy into the darkness, listening for movement from the demon.  Then as a bonus action, he directs his unseen servant to stand in between Aisha and the darkness / demon, hopefully to block any tentacle or attack headed her way.  

Eldritch blast : 20 to hit (with disadv), for  7 points of force damage.  

Eldritch blast : 9 to hit (with disadv), for  13 points of force damage.  

He backs up a little further, 15 feet away.  

Duncan manages to save, taking less damage from the roar, but is now encased in total darkness. Unable to really do anything in the darkness, Duncan will take a few steps back out towards where the others are, stopping between them and the darkness, ready if the creature should approach.

Wisdom Save: 12

Pushing through the pain of the attack Aisha focuses on the prayer.

Round 3

Zarkar moves out of the darkness and attacks Duncan 2x

Claw - Attack: 8 Damage: 9

Bite - Attack: 17 Damage: 11

Poison damage - 1

If bitten roll Con Save DC 14. On fail you are poisoned. You can re-roll each round to shake off the poison

Now its the party's turn

Kasbis's first attack hits from last round

Aisha has been training her entire life, knowing somewhere inside of herself that a day like this might come. Despite the stress of the situation she remains calm and stays focused.

Kasbis focuses two more beams of energy to strike the creature, now that some of it is visible.  

Eldritch blast : 22 to hit, for 5 force damage and 3 thunder damage.  

Eldritch blast : 23 to hit, for 7 points of force damage.  

Duncan reacts quickly and attacks as the demon approaches him. He then angain amazingly manages to dodge both swings from it, responding with his own flurry.

reaction:
Attack: 25 Damage: 7
action:
Attack: 23 Damage: 9
Attack: 24 Damage: 8
bonus:
Attack: 18 Damage: 4

Round 4

Zarkar attacks Duncan 2x

Claw - Attack: 8 Damage: 7

Bite - Attack: 13 Damage: 14

Poison damage - 4

If bitten roll Con Save DC 14. On fail you are poisoned.