Acid damage for Tasha's Caustic Brew: 7

The prize was a grey bag of tricks

A chilled spectral hand is summoned from the ether, grasping at mephit #3, draining life force and vitality from the elemental creature.

Mephits Turn!

The Mephits fly forward on their steaming wings, clawing at you with their boiling talons

Claw attack #1 VS. Weaver: 22 to hit, 2 Fire plus 4 Slashing

Claw attack #2 VS. Ooboron: Unable to parse dice roll. to hit, 1 Fire plus 4 Slashing

Claw attack #3 VS. Elsenia: 3 to hit, 3 Fire plus 2 Slashing

Claw attack #4 VS. Theo: 18 to hit, 4 Fire plus 2 Slashing

Theo, then Weaver

Theo, GO!

It says unable to parse dice roll for Ooborons attack, so I'll roll that again: 10

@DM: I'm assuming the WIS save of 7 in post #299 was the mephit trying to save from my vicious mockery, which would have been a fail. That means one of the mephits should be attacking at disadvantage. And I'm hoping it was the one that attacked Elsenia since hers was the only one that hit. :)

Theodore uses Cunning Action to Disengage from the one near him and moves next to Elsenia to attack #3

Stabby! Attack: 10 Damage: 10

Ooboron, for simplicities sake, the one that attacked you was the one with disadvantage. If you check the attack roll in post #302 was at disadvantage. If you want to specify a number next time, feel free too.

Theo rushes forward, hopping on his rabbit legs, and stabs with his blade, piercing the Steam Mephit, which explodes in a burst of steam. Elsenia & Theo, Make a DC 10 Dex Save or take 1 Fire damage.

ROUND TWO!

Weaver, then Elsenia

Weaver, GO!

(Weaver maintains concentration on Tasha's Caustic Brew, at the start of their turn, the mephits will again take 2d4 acid damage, and they'll continue to do so until they take an action to wipe themselves off)

Weaver notices that the 'energy drink' she mistakenly unleashed on the mephits is sticky and cloying, and she thinks to herself "Hmm, this could make a good adhesive!  Or a solvent!  Maybe both?" Her eyes widen as she realizes she may have just invented a Gelatinous Cube in a bottle.  "I've got to write this down!"  As she starts fiddling with her new invention, an automatic note taker, a familiar brass contraption on her wrist springs open, and a pencil materializes briefly before being launched at high velocity toward the closest mephit.  "Oops!"

(Repeating shot light crossbow attack at the closest mephit)

Attack: 25 Damage: 6

The pencil flies forward, sticking in one of the Mephits. The Mephit screams in pain as the projectile digs into it.

Elsenia, then Ooboron

Elsenia, GO!

Dex save 13

Theo is ducks out of the way as the creature explodes, "AH! I wasn't expecting that. Be careful guys they have a nasty pop when you kill them!"

Well going to school is ending up to be more interesting than ever he thought.

Dex Save - 12

Elsenia cringes as the mephit explodes right in her face. "Ahh!" she lets out a scream, more startled than hurt. She's never been a fan of fire, and she's especially not a fan of these mephits!

She points her staff toward another mephit and a stream of sickly green poison sprays over the creature. It must make a constitution save of 14 or take 1 poison damage!

@DM: Missed that. Sorry for questioning you!

Ooboron cowers as the mephits approach. He gasps as one of the creatures rips through and slightly singes his tunic, but he's glad his thick skin protects him from any damage to his person. As the others quickly begin attacking, the loxodon hesitantly grabs the small axe he carries in his belt. His father made him promise he would use it if he found himself in danger. Ooboron bites his lip and swings the weapon at the mephit.

Attack: 21 Damage: 4

As Theo ducks out of the way of the exploding Mephit, Elsenia spins her staff and a puff of noxious green fog envelops another Mephit. Interestingly, the creature breathes in the poison, slurping it up with an awful sound, as if a reverse sneeze, and does not seem affected by the poison at all.

Ooboron summons his courage, shakily hefting his axe, and with a mighty trumpet, brings it down upon one of the Mephit's heads. It strikes true, and the creature yelps and backs away, now scared of the massive loxodon with the sharp thing.

Mephit's Turn!

Acid Damage for Tasha's Caustic Brew: 6

One of the Mephits succumb to the burning acid, melting in a puddle of liquids and gasses with a ghastly screech, then with a poof, it explodes. Ooboron & Weaver, make a DC 10 DEX save or take 6 fire damage

The remaining two Mephits look at each other, then let out a high-pitched, primal scream, and charge forward, bubbling claws outstretched:

Mephit #1: Claw Attack VS. Weaver: 13 to hit, 6 Fire and Slashing damage

Mephit #4: Claw Attack VS. Theo: 19 to hit, 5 Fire and Slashing damage

Theo, then Weaver, then Elsenia

Theo, GO!

Weaver's Dex save: 15

Ooboron attempts to dance out of the way.

Dex save: 12

Theo tries to stab the one right in front of him.

Shortsword stab Attack: 20 Damage: 13

Draw dagger and stab Attack: 12 Damage: 3

Weaver is surprised, this is spicy steam indeed! Realizing she can't take too many more hits like the last one, she reaches deep into her satchel and pulls out a canister with what sounds like a marble inside it. She pulls out a small screwdriver and affixes a nozzle to it, then sprays it on her wounds, which immediately begin to knit themselves closed. 

(Casting Cure Wounds to regain 7 HP) 

Elsenia backs away from the mephits as far as she is able to while still being able to see them. She doesn't want to risk any burns when they explode. Then she motions her staff toward one of the remaining mephits. This time she will cast another chill touch at it since apparently they seem to like poison, which is alarming.

Attack: 16 Damage: 5

Theo draws his dual blades, and stabs one of the Mephits, who howls in pain and melts from the vicious strike and bursts in a grisly blast. Theo, you know the drill. DC 10 DEX save or 7 fire damage. His second strike digs into the remaining Mephit, lodging in its ribs before being pulled out in a blood display.

Weaver pulls out another contraption, and a white goo sprays over her wounds, sealing them closed

Elsenia backs away, fending off the creatures with her staff. With a flourish, she sends a ghostly hand of death forward, invoking the power of her homeland, the ShadowFell. It latches onto the remaining Mephit, and it screams as it's flesh withers and rots. The final Mephit looks almost dead, blood, gore, and rot covering their body, as well as bubbling acid.

Ooboron, GO!

Ooboron scowls. Not only are these creature scary, but the remaining one looks gruesome! Never has he seen such a horrible sight. But he swings his axe again, hoping to put an end to this crazy scene.

Attack: 9 Damage: 2