If the black puddings are still alive after receiving Necrotic Damage from the spell, Maerwyn will attempt to inflict fatal damage to the one with the highest hitpoint. She thanks Grom for his quick-witted assistance, then she reloads the Light Crossbow with more ammunitions and continues to attack.

Attack

Light Crossbow[Ranged]: Attack: 26 Damage: 1

Extra Attack: Attack: 26 Damage: 3

Quote from InkedBee >>

If the black puddings are still alive after receiving Necrotic Damage from the spell, Maerwyn will attempt to inflict fatal damage to the one with the highest hitpoint. She thanks Grom for his quick-witted assistance, then she reloads the Light Crossbow with more ammunitions and continues to attack.

Attack

Light Crossbow[Ranged]: Attack: 26 Damage: 1

Extra Attack: Attack: 26 Damage: 3

 Both hit, but they don't seem very wounded. The bolts get destroyed as soon as they hit the black pudding. They continue climbing, now 60 ft. up.

Quote from Orange20 >>

 Both hit, but they don't seem very wounded. The bolts get destroyed as soon as they hit the black pudding. They continue climbing, now 60 ft. up.

Maerwyn will cast Slow in order to reduce the movement speed of the black puddings. The spell affects both of the creatures within a cubic range of 40 feet, and the time around these creatures is altered. 

Each target must succeed on a DC 15 Wisdom Saving Throws or be affected by this spell for the duration. An affected target's speed is halved, it takes a −2 penalty to AC and Dexterity saving throws, and it can't use reactions.

14

18

((Transmuted Spell fireball changed to deal thunder damage: each must make a Dex save vs DC 19 with -2 penalty due to Slow or take 33 thunder damage.))

"Fly away if they get close, don't let them touch you." Since that they apparently didn't take all that much damage, Grom raised his staff and sent an energy blast at them.

Maerwyn will maintain a safe distance from the Black Puddings, then hover over the entrance of the pit to investigate if the pool of acid has something to do with the Oozes and Black Puddings.

Investigation 25

Quote from InkedBee >>

Maerwyn will maintain a safe distance from the Black Puddings, then hover over the entrance of the pit to investigate if the pool of acid has something to do with the Oozes and Black Puddings.

Investigation 25

 When she looks closer, she can see that the pool of acid is where the oozes seem to come from.

Quote from ikarbino >>

((Transmuted Spell fireball changed to deal thunder damage: each must make a Dex save vs DC 19 with -2 penalty due to Slow or take 33 thunder damage.))

"Fly away if they get close, don't let them touch you." Since that they apparently didn't take all that much damage, Grom raised his staff and sent an energy blast at them.

 *They auto-fail.*

They get harmed by it, but they're still alive. They continue climbing up, now 25 feet from the opening.

Maerwyn realizes that these Ooze-folk and Black Pudding has Immunity to Acid Damage since these creatures have literally climbed up from a pool of acid. The Crossbow Bolts get destroyed which explains that these non-magical weapon can deal trivial damage to these creatures.

The Blood-Hunter will use her Grappling Hook to Grapple the Black Pudding which is closer to the entrance of the pit, then she will attempt to pin the creature so that it remains Restrained.

Grapple Check: 3

Grapple Check (Restrain): 9

The Black Pudding must make another Dexterity Saving Throw because of the effect from Slow that has been cast earlier.

(Edit: The Grappling Pin is not the intended item, it's a Grappling Hook and I edited it.)

Dusk will float over - just in time to witness Maerwyn grapple one of the oozes right after Grom had said not to touch them. 

Shaking away the desire to palm his face, Dusk looks at the nearest ooze and simply mutters, "torri'r meddwl."

Break the Mind. Casting Mind Sliver: target must make DC19 Intelligence save or take 14 Psychic Damage and the next saving throw the creature must make before the end of Dusk's next turn has a -2 penalty. This happens after Maerwyn's grapple so it will not apply to that. 

Quote from InkedBee >>

Maerwyn realizes that these Ooze-folk and Black Pudding has Immunity to Acid Damage since these creatures have literally climbed up from a pool of acid. The Crossbow Bolts get destroyed which explains that these non-magical weapon can deal trivial damage to these creatures.

The Blood-Hunter will use her Grappling Hook to Grapple the Black Pudding which is closer to the entrance of the pit, then she will attempt to pin the creature so that it remains Restrained.

Grapple Check: 3

Grapple Check (Restrain): 9

The Black Pudding must make another Dexterity Saving Throw because of the effect from Slow that has been cast earlier.

(Edit: The Grappling Pin is not the intended item, it's a Grappling Hook and I edited it.)

 18

 6

STR: 22

Quote from Orange20 >>

Quote from InkedBee >>

Maerwyn realizes that these Ooze-folk and Black Pudding has Immunity to Acid Damage since these creatures have literally climbed up from a pool of acid. The Crossbow Bolts get destroyed which explains that these non-magical weapon can deal trivial damage to these creatures.

The Blood-Hunter will use her Grappling Hook to Grapple the Black Pudding which is closer to the entrance of the pit, then she will attempt to pin the creature so that it remains Restrained.

Grapple Check: 3

Grapple Check (Restrain): 9

The Black Pudding must make another Dexterity Saving Throw because of the effect from Slow that has been cast earlier.

(Edit: The Grappling Pin is not the intended item, it's a Grappling Hook and I edited it.)

 7

 12

STR: 5

 They aren't grappled and still slowed down.

Quote from Cyb3rM1nd >>

Dusk will float over - just in time to witness Maerwyn grapple one of the oozes right after Grom had said not to touch them. 

Shaking away the desire to palm his face, Dusk looks at the nearest ooze and simply mutters, "torri'r meddwl."

Break the Mind. Casting Mind Sliver: target must make DC19 Intelligence save or take 14 Psychic Damage and the next saving throw the creature must make before the end of Dusk's next turn has a -2 penalty. This happens after Maerwyn's grapple so it will not apply to that. 

 *They fail.*

They take the damage, but both are still standing.

Magron will cast sword burst in such a way that he hopes to get two of them. DC19 dex save for 13 damage

Quote from Secretfool >>

Magron will cast sword burst in such a way that he hopes to get two of them. DC19 dex save for 13 damage

 *They aren't in SB range.*

(@Orange20, what's the radius or area of the entrance of the pit?)

Quote from InkedBee >>

(@Orange20, what's the radius or area of the entrance of the pit?)

 The radius is 3.5 feet.

Maerwyn will cast Minor Illusion to create the image of an trap door inside the passage so that it's partially blocking the path (5 feet cube, length of the diagonal is around 8 feet) within the range of 30 feet. Investigation check against Spell Save DC 16 should reveal it as an illusion. Both of the creatures must make Wisdom Saving Throws to ignore the effect of the previously cast spell Slow.

If one of the creatures attempt to pass through it, she's going to use her bonus action to Grapple it with her Grappling Hook.

Grapple Check: 19

OOC:

Slow is Wisdom.

Grappling Hooks can't grapple people. They're used for climbing. The only way to make it grapple is to have it swing around the target and latch back onto itself - which, given these are Large creatures in a narrow shaft, would be physically impossible. 

Quote from InkedBee >>

Maerwyn will cast Minor Illusion to create the image of an trap door inside the passage so that it's partially blocking the path (5 feet cube, length of the diagonal is around 8 feet) within the range of 30 feet. Investigation check against Spell Save DC 16 should reveal it as an illusion. Both of the creatures must make Dexterity Saving Throws to ignore the effect of the previously cast spell Slow.

If one of the creatures attempt to pass through it, she's going to use her bonus action to Grapple it with her Grappling Hook.

Grapple Check: 19

 Saves: 10. 2.