Ooboron tugs at the dress and fails to pull it off. Seeing his efforts not having much effect, he instead tries helping his friend escape, encouraging the little thief to do what he does best: escape from sticky (or should I say dressy?) situations. 

The natural skill, practised talent, and power of friendship which is granted by Ooboron combines to make Theo's escape easier than expected. He manages to wriggle out of the dress, his little rabbit legs propelling him into the air. For a second, he seems to float there, and then falls back to earth

Weaver & Elsenia GO! Theo also still has his movement and bonus action, so he can use those if he wants

Weaver doesn't want to make a splashy, acidic mess in here, so she'll keep it limited to physical attacks for now. She aims in with her crossbow, trying to pin the dress to a wall where it won't be able to come at them again - 

Attack: 13 Damage: 9

Weaver's crossbow bolts glances off the wing of the KBD, causing it to "stumble" backwards a few feet, though it deals no actual damage. 

Elsenia and Theo (if he wants to), GO!

Theo hopes his friends can take down the magical whatsit. 

OOC: Nothing much to do right now - no useful bonus actions for the moment.

Elsenia remembers their battle against the strange chest that had come to life, and she decides to use her favorite spell, Entangle, to hopefully pin the dress in place and make it easier to hack to pieces.

STR save: 14

Vines erupt from the floor, worming their way up through the floors of the mansion, bursting out and entangling those around it. As it is an area of effect spell, I would ask that Theo and Ooboron, who have both been in melee with the KBD, make the STR save (I believe DC 14?)

The KBD manages to not be caught by the twisting vines, floating in the air above the restraining plants. It lands back down, and flares out the cuffs of its wrists, summoning the primal winds which are harnessed to keep it aloft, and blasts them out in a cone of gusting air, sending Elsenia and Weaver tumbling backwards. Can both of you make a DC 13 STR save or you fall Prone, are pushed back 10ft, and take 4 Bludgeoning damage as you slam into the wall.

It is now the parties turn! I need a STR save from everyone for their various reasons, and you all can try to finish this thing off.

Strength Save - 7

Elsenia flies backward into the wall as the dress creates a gust of wind. It was able to evade her magical vines. "Ow!" she cries out and rubs the back of her head when she is able to stand. "Stupid dress."

She stops concentrating on her vines spell and instead tries to warp the dress with a little more necrotic magic.

Attack: 10 Damage: 8

OOF!

Weaver rolled a 3 (in the game log) for her save, she's prone and not very happy about it.  She stands up, and takes more careful aim with her crossbow this time.  "So you guys know, my constructs are all going to be more polite than this one!"

Attack: 14 Damage: 7

Theo has an EEK! reaction as the vines try to grab him but thankfully they vanish into the aether.

Back to business, he draws his side dagger and makes two attacks on the dress.

Shortsword Attack: 23 Damage: 5

Off-hand Dagger Attack: 10 Damage: 3

Sneak Attack 6

Both Elsenia and Weaver are knocked backwards, but they recover in time to send forth bolts of mechanical ingenuity and a ghostly hand. The ghostly hand flies forward, but the dark energy is reflected by the unliving energy of the dress, as the attack misses. Weaver sends forth another bolt, but luck is just not with her today, as it shatters against the wall after nearly giving Theo a haircut.

Theo leaps away from the stray bolt, before drawing his other blade and rushing forward, dodging the attacks of the KBD. he sends both his shortsword and dagger forward in a duel thrust. The KBD prioritises protecting from the larger weapon and deflects the longer blade, though the dagger makes it through and tears a hole right in the bodice of the dress. Now no self-respecting lady will ever wear it again. The dress, weakened by the onslaught, is almost done for

Ooboron, summon your courage and finish it off!

As the vines begin rising from the floorboards at his feet, the loxodon stomps quickly, his big feet beating back the plants surprisingly (17 in game log). Furrowing his brow, he draws his axe once again and swings at the menacing dress. "Back!"

Attack 8, Damage 2

The KBD does in fact move back. And out of the way of Ooboron's axe swing. Man, this things AC is high.

KBD's turn!

The KBD, sick of all of you, flaps its bladed wings, rising into the air. It floats high above you, then flares its skirts out and comes crashing downwards, causing a massive cloud of dust to rise from the floor. Everyone make a DC 11 CON save or be blinded

Parties Turn! Come on! You're so close!

Con save: 23 (nat 20! in the game log)

Weaver sees what the dress is about to do, and drops her goggles over her eyes just in time!  The crossbow isn't working, though, so she'll resort to the messy option.  "Theo!  Ooby!  Get out of the way!"  and she shakes up a small canister before popping the top and unleashing a stream of Tasha's Caustic Brew at the dress.  DC14 Dex save, or take 5 acid damage (again, in the log).

Con save 17

Dex save 7

Theodore is blinded by blowing dust a debris and leaps the wrong way when he hears Weaver call out. Staggering on his feet, he reaches out with his weapons hoping to score a hit.

Shortsword Attack: 12 Damage: 10

Dagger Attack: 8 Damage: 2

DEX save: 22

Weaver, getting tired of the crossbow, brings out the big guns. Oozing acid sprays everywhere

And a fail! The KBD is covered in glop and melts to the floor, and then a hole melts into the floor. You look down and can see hallway below you. Whoops.

the KBD is destroyed!