Both Merrow are Charmed and Incapacitated

The rest of Group 1 still up

Theldrin steps up behind Khessa where he can get a better view of the Merrow approaching Coriana, then aims rays of fire.

Scorching Ray
Attack: 8 Damage: 9
Attack: 17 Damage: 4
Attack: 10 Damage: 9

Coriana swims over and attacks the merrow closest to her, resummoning her hex from the abberation fight.

Bonus: Hex.
Move: to Merrow.
Longsword: 22 Damage: 15 necrotic.
Longsword: 13 Damage: 13 necrotic.

Heroic Inspiration: Reroll second Longsword - 20

(OOC: I can't figure out how to add a photo so I am adding a link to Google Photos. https://photos.app.goo.gl/hWbAL6LaDBicJaXk7. Also this is my first time casting Conjure Animals so I think based on my interpretation of the spell I am using it right.)

Round 1

Syllen summons a pack of wolf spirits next to Khessa and moves 10 feet to the west. As Syllen moves the spirits also move to a space next to Coriana. As the spirits move within range of the two Merrows not affected by Hypnotic Pattern the power of the spell lashes out at them. Syllen also manifests the power of the Archer and attacks the same Merrow as Coriana.

Action: Cast Conjure Animals. DC 15 Dex or take 23 Slashing Damage (If they end their turn within 10 feet of the spirits they will take more damage.) 

BA: Luminous Arrow Hit: 26 Damage: 10 Radient

Move: 10 feet west

Concentration: Conjure Animals round 1 of 10

Avery engages the closest Merrow: Attack: 24 Damage: Unable to parse dice roll.; Attack: 8 Damage: 14

Only one of Theldrin's rays hit, the other two sizzling on the water. Coriana's sword is far more effective, slicing deep slashes into the Merrow, filling the water around her with blue-black blood. The Merrow then make DEX Saves against the summoned wolves:

Merrow 3 DEX Save: 5

Merrow 4 DEX Save: 10

Syllen's wolves fail to get their teeth into the underwater Merrow, but his arrow sinks into the side of one of them. Avery steps forward and hacks into Merrow 4 with his sword. The Merrow then move to get away from the wolves and attack their targets, while Merrow 1 and 2 are unable to do anything.

Merrow Bite against Coriana Attack: 13 Damage: 5 Piercing and Coriana is Poisoned till the end of the creatures next turn.

Merrow bite against Avery Attack: 18 Damage: 5 Piercing and Avery is Poisoned till the end of the creatures next turn.

The Merrow make their second attacks with Harpoons, with advantage against the Poisoned Avery:

Harpoon against Coriana Attack: 17 Damage: 14 Piercing

Harpoon against Avery Attack: 25 Damage: 13 Piercing

Even more horrific, an alien form of writhing tentacles, fishy scales, and glowing malevolent eyes rises to the surface about 20 feet from the bridge. Coriana feels the pulsing now deep in her chest, almost a panic attack setting in. The creature assesses the situation and immediately uses it's Dominate Mind ability on Xanrym:

Xanrym makes a DC 16 WIS Save or is Charmed by the fish-aberration and must obey it until the domination is broken: 4

Xanrym is forced to immediately drop the Hypnotic Pattern and will act in accordance with his new master this turn. The rest of you are up, Merrow 1 and 2 are now free while 3 and 4 are looking really sliced up by Coriana and Avery. This new monstrosity has Xanrym in it's mental grip, and Avery is still Poisoned.

Theldrin aims a Fireball at the Merrow next to the fish abomination, hoping to include both the abomination and the Merrow to the west within the blast radius.

Fireball: 25
Dex 15 Save for half damage

Merrow 1 DEX Save: 13

Merrow 2 DEX Save: 10

Fish Aberration DEX Save: 12

All the creatures take the full brunt of the Fireball, but you notice that when the flames hit the Fish Aberration, it's form flickers in and out of existence for a moment. The flames seemed to have hurt it, but something is strange about it's appearance.

The rest of you are still up, Xanrym is dominated, while Avery is Poisoned.

The Aberration ends its turn or moves within 10 feet of the spirits so it needs to make a DC 15 dex save or take 7 slashing damage.

Turn 2

Syllen will move 5 feet east and move the spirits 30 feet.

Spirits movement

1) 5 feet south east

2) 10 feet North West

3) 10 feet West, 5 feet south 

That should hit everything but the West most merrow. DC 15 Dex Save or take 12 slashing damage from all of the other enemies.

Syllen will attack the merrow that looks most hurt

Action: True Strike Hit: 10 Damage: 14 Radiant

BA: Luminous Arrow Hit: 25 Damage: 7 Radiant

Aberration DEX Save 1 or 7 Damage: 22

Aberration DEX Save 2 or 12 Damage: 18

Merrow 2 DEX Save: 5

Merrow 3 DEX Save: 20

Merrow 4 DEX Save: 13

Syllen wipes out both Merrow 4 and Merrow 2 with his Luminous arrow. Khessa, Coriana, and Avery still up. Avery is Poisoned and Xanrym is Dominated.

Quote from drumdigby >>

Syllen's wolves fail to get their teeth into the underwater Merrow, but his arrow sinks into the side of one of them. Avery steps forward and hacks into Merrow 4 with his sword. The Merrow then move to get away from the wolves and attack their targets, while Merrow 1 and 2 are unable to do anything.

Merrow Bite against Coriana Attack: 13 Damage: 5 Piercing and Coriana is Poisoned till the end of the creatures next turn.

Merrow bite against Avery Attack: 18 Damage: 5 Piercing and Avery is Poisoned till the end of the creatures next turn.

 Did you take into account my necklace of adaption on the poison save?

Avery will attempt to remove the poison effect: 13

He continues in battle: Attack: 10 Damage: 14; Attack: 15 Damage: 14