Kaltent keeps an eye out behind them while Shift opens (or tries to open) the door.

Zinn joins Shift by walking over to the Festive Hall and examining the entry way. 

OOC: 

@Paradox no worries bud, Zinn just wants to keep his options open, but no reason we can't do both ;)

Climbing the stairs, the entire party arrives at the open entrance to an old Festival Hall with a 30' high arched ceiling. The walls are decorated with bas-reliefs of dwarves singing and drinking. A dozen empty iron torch brackets are mounted to the north and south walls at 10-foot intervals.

Two rust monsters are fighting over a rusted steel helmet in the middle of this room, casting it about as they knock each other around. Neither seems to notice the party enter the room. There is a door on the other side of the hall that is presently closed and a long hallway behind them leading east.

Zinn watches the Rust monsters blankly for a few moments before dryly stating "I see no reason to disturb these two, they seem like they could be content here for a century or more if left to their own devices. Let us do just that, and head east to see if we can't hunt down this Nadia we've heard so much about..."

Shift nods his agreement and quietly replies,

"Yeah, no need to tangle with those bloody metal thieves."

Shift quietly backs out of the hall and starts heading east, looking back over his shoulder to make sure his friends are following.

Bronx looks a little disappointed but follows his mates eastward. The passage is long and it winds back and forth before coming to an intersection. According to their map, moving straight takes them back to the goblin market. Heading south takes them towards Nadia and some parts unknown. Just as they turn the corner, they are met with a floating monstrosity. Its skin is desiccated and its eyes cloudy. A white circle with spokes has been painted on its face around its primary eye. The undead beholder immediately moves to attack.

Initiative:

 (Everyone may go in any order.)

Kaltent darts forward to stab at the beholder with his rapier before backing away again to make space for his allies.

Move into melee

Booming Blade: Attack: 10 Damage: 11 + 3 thunder + 7 (sneak attack).  Plus 11 thunder damage if he moves before my next turn.

Move back again as far as possible (no AoO due to Fancy Footwork)

Shift's eyes go wide at the sight of the desiccated beholder.

Shift decides to try this new Tan Bag of Tricks, pulling out a little ball of fuzz and tossing it in the direction of the enemy.

Out pops...(6..oops, you already rolled a 2!)...an Ape!

The fuzzy object transforms as it touches the ground, becoming an Ape.

Shift gives a non-committal tilt of the head, not sure if this will be useful or not, before moving forward and transforming into a large Brown Bear, placing himself in the line of fire between the Rotting Beholder and the others behind him.

The Ape looks around itself in mild confusion before spotting the Rotting Beholder and scampers over to hide behind Shift's bulky form.

Zinn shrieks with disgust at the creature, and hurriedly waves his hands and conjures a ball of flames. He pitches his spell at the monster and quickly repeats the motion, uttering Draconic incantations.

Scorching Ray Attack: 9 Damage: 11

Scorching Ray Attack: 21 Damage: 8

Scorching Ray Attack: 24 Damage: 8

Kaltent misses but Zinn strikes the creature with two of his rays.

The beholder (4) shoots a ray from one of its eye stalks against 6 Bronx. CON(14) check: 23 Bronx takes the full 12 necrotic damage.

(Bronx never expended hit dice during the short rest? 29)

Bronx roars a spell out, casting guiding bolt (second level) at the creature.

Guiding bolt Attack: 8 Damage: 18

Four women, two men, and five bugbears coming running in from the next room, all drawing their weapons.

(Everyone may go in any order. I will have a map up shortly.)

Map:

Shift roars at the Ape, instructing it to stop hiding and fight, before stepping forward and attacking the Desiccated Beholder himself.

The Ape steps around Shift large bear ass and attempts to hammer the Beholder alongside its master.

Zinn startles at the appearance of so many armed opponents in the crowded hallway, and attempts to speak to the group of human females. ”What’s all this then?? We seek a parlay with Nadia of the Xanathar! Are you with her or are ye minions of this wretched beast!? Speak some sense if you’re not in league with this undead horror! Or suffer our wrath!” He waves his staff threateningly at the group.

Intimidation: 25

”Shield your eyes and avert your gaze...” Zinn says through gritted teeth in a low voice so only his companions can hear him.

Zinn will cast the spell Hypnotic Pattern if any of the Humanoids take hostile actions against Zinn or his companions.

One of the humans snarls, saying, "Death to the intruders!" and Zinn casts his spell.

DM shield:

 (Kaltent and Bronx are up.)

Paging Kaltent.

(Sorry, totally missed that it was my turn again...)

Kaltent looks away for a moment at Zinn's warning, then after the spell has gone looks back towards their foes.  He curses the beholder (actual curse, not just mouthing off :P.  Put Hexblade's Curse on him) then steps forward to stab at it again (staying out of melee range of any other enemies) before retreating back behind his friends.

Booming Blade: Attack: 13 Damage: 11 + 3 thunder + 10 (sneak attack).  Plus 9 thunder damage if he moves before my next turn.

Move back again as far as possible (no AoO due to Fancy Footwork)

Kaltent effortlessly slashes his blade through the momentarily distracted beholder, causing a dazzling display of desiccated tissue to spray around the room. (Crit hit roll: 70...no effect since it cannot be knocked prone.)

(I also forgot a crit fumble roll for Shift: 48)

Shift and his ape each get a hit in almost simultaneously, though Shift's gaze cannot help but be drawn to the overwhelming number of people that have entered the room. (Next attack is with disadvantage.)

Bronx is also somewhat stunned at the in-pouring of new foes. He walks forward, chanting as he takes his place just south of the beholder. He finishes chanting his spell and dozens of mall, glowing and flying fiends leap out around him, then zip away to pester the combatants in the room.

(Bronx has cast Spirit Guardians.)

The foes must all fend off the new fiends. WIS(14) checks:

• BZ: 16 or suffer 16 (half on a success)
• N: 20 or suffer 9 (half on a success)
• B1: 4 or suffer 11 (half on a success)
• B2: 12 or suffer 9 (half on a success)
• B3: 10 or suffer 13 (half on a success)
• B4: 17 or suffer 12 (half on a success)
• B5: 1 or suffer 6 (half on a success)
• T3: 11 or suffer 10 (half on a success)
• T4: 14 or suffer 12 (half on a success)
• T5: 19 or suffer 16 (half on a success)