Another smirk from the fighter to the hag. "Let's test that," he countered as he swung again, lunging in to strike upward with the lower part of his blade.

FREE: Use Great Weapon Master to give -5 to his next attack roll, +10 to damage
ACTION: Attack the hag; Trip Attack on a hit (DC 13 STR Save to avoid being knocked prone,) and using advantage from Silvery Barbs
* Greatsword Slash - Attack: 14, Magical Slashing Damage: 25 (plus 10 extra dmg on crit)

Quote from Scott_R_Simmons >>

Fuego:

With the others crowding the Hag, Fuego keeps an eye one the general location where the mephit disappeared, ready to throw a ball of flame at it if it resurfaces.

Readied Produce Flame Attack (that damage rolls of 1 as 2, ignore fire resistance):  Attack: 13 Damage: 2

 Make that 4 points of fire damage if it hits as Fuego invokes Genie’s Wrath!

Thrudor impressed with his new companions and how they are handling themselves decides his best course of action is to hurl another bolt of green light at the hag

Guiding Bolt Attack: 20 Damage: 10

As the others continue their onslaught Phait drives a psychic spike towards the hag.

Mind Sliver

Damage: 3 psychic

Save DC: INT 15, on fail takes damage and -1d4 to next save

Hag INT save: 21

Minus 3 to next save.

(Just waiting on Cunning)

Thanks to his rage Cunning resists some of the damage, and it triggers a Hellish Rebuke for 21 fire damage (Dex 10 save for ½)

He then takes another swing with the maul

Attack 24 (nat 20)

Damage 15 + 8 lightning (DC 13 str save).

Hag Dex Save: 9

The hag screams as her body rapidly rots. But dark energy begins to surround her and she continues to live: In a weakened, zombified body. She bites Cunning viciously, 23 to hit, 8 piercing and 3 poison damage.

The mephit hears the cry, jumping up from below Phait's feet and attempting to blind him with dust. DC 12 Constitution saving throw to resist being blinded. Phait may redo his saving throw at the end of each of his turns, ending the condition on a success. He then lunges towards Titus, prepared for his next strike.

Titus couldn't help but chuckle. The mephit was attacking him? Nothing more than a distraction, as far as the fighter was concerned; he side-stepped the creature and once again brought his blade down on the hag.

ACTION: Attack the hag; Trip Attack on a hit (DC 13 STR Save to avoid being knocked prone)
* Greatsword Slash - Attack: 22, Magical Slashing Damage: 15 (plus 16 extra dmg on crit)
BONUS: If the Action crits or brings the hag down to 0 HP, Titus will use his Great Weapon Master feat to make a bonus attack
* Greatsword Slash - Attack: 13, Magical Slashing Damage: 19 (plus 15 extra dmg on crit)

(( @DM: I'm not sure how many times Titus has actually hit? Just trying to keep track of his maneuver dice. ))

Thrudor waiting for the Mephit to reappear to end its time in this plane gets his chance.

He hurls a flame at it 

Attack: 9 Damage: 5

Phait Con Save: 8+6 = 14

Phait eyes the mephit and taunts, "You I'll deal with late, annoying gnat!" He eyes the undead hag and then turns to Fuego, "Think you could help put out a fire if needs be? In my eyes, undead must burn."

If Fuego approves he'll cast Create Bonfire on the hag.

Damage: 8 fire

DEX Savce DC 15 (with -1d4 from prior mind sliver)

Otherwise will do another mind sliver (feel free to roll the 1d6 psychic damage, DC 15 INT)

(Fuego had a readied action to fry the Mephit when it reappeared—did that damage (4 points fire) do enough to kill it before it could attack?)

(Titus, She has the same armor class as a Green Hag, 17. You've hit twice.)

The mephit bursts into flame, causing it to explode upon its death. Phait and everyone within 5 feet of him must succeed in a DC 12 Constitution saving throw to resist being blinded. They may redo his saving throw at the end of each of his turns, ending the condition on a success.

Hag Dex save: 16

The hag's whole body has rotted, but she still resists death. Half of her left arm falls to the ground and withers to dust within seconds. The few people who haven't fled the bar begin cheering.

DC 15 Wisdom save to resist death: 18

The hag is still alive, but barely. She'll have to repeat this save each time she takes damage, so Cunning might have the honor of slaying the hag.

(In case anyone is confused, it's a Wisdom save because she's surviving through magic. Also, she's Undead right now, not Fey, in case anyone needs to know that.)

Fuego:

Seeing his flame kill the mephit (from his readied action), Fuego looks in horror at the now-undead Hag.  He calls down holy flame this time, hoping the divine radiance can destroy this undead!

Sacred Flame, DC 15 Dexterity Save to Avoid:  3

Smiling at Phait, Fuego says, “The flame does indeed answer to my call.”

Phait CON save from ecploding mephit: 21

Cunning ignore the exploding mephit (con 13) and takes another enraged swing at what's left of the hag.

Attack 21 Damage 7+2

DC 15 Wisdom save to resist death: 12