Jurgen, thoroughly unnerved by the goblin's whispers, sprints for cover in the far stairwell.

Bryony ignores the psychic detonation and urges Boona to consider taking the last goblin, convulsing helplessly on the floor, as a prisoner.

Fergus runs south into the Mess Hall. Three rectangular stone tables stretch the length of the room, along with several sets of stone benches. Bowls full of gritty white porridge and dirty, bent spoons are strewn across the tables or dumped on the floor, where the fleeing brawler sent them flying. On the east side of the room, a serving window provides a view into another room (a kitchen?) There is but a single fleeing goblin visible, the half-crushed brawler, still scrambling to escape the grasp of the massive serpent. Fergus launches a mote of luminous music at the strange, fleeing goblinoid, and it goes down hard near the southeast exit. Fergus can feel the psychic detonation of the dying creature, but he's too far away to be harmed by it. It is dead.

Quinn lifts his bow but then reconsiders as he sees the brawler go down. (He may redo his turn, but if it involves an attack he must keep that roll.)

Boona tries to crush the big goblin on the floor, but even in its vulnerable state, it manages to roll out of the way of her hefty maul.
 
Jurgen (now recovered from his sudden strange reaction), Jorzu, and Bryony may act (and Quinn may repost his.)

Jorzu vanishes to the southwest. Laiti joins him and similarly vanishes. The laughing from the goblin stops abruptly. Jorzu can see an east-west stone corridor, dimly lit in that eerie blue light. 

Hugo tries to bite the prone goblin (he can have Advantage on that) but (so far) fails. DC14 STR Save: 19 or be crushed and grappled...

Jurgen and Bryony may act. (Quinn may repost his, and Hugo may make an advantage bite roll against his prone opponent.)

Jurgen regains his senses and runs next to Quinn. 

(If possible he would attack)

Boona looks down seemingly confused as to how she missed the goblin, shrugs and tries again.

Attack: 28 Damage: 24

Seeing everyone else continuing to attack the goblin, Bryony sighs and attacks it too, hoping to put it out of its misery quickly. She supposes the goblin probably wouldn't have told them anything anyway. She tries not to feel too bad seeing as how goblins have been responsible for a lot of deaths recently, and they've even kidnapped her family! The halfling moves through Boona's legs to get to the goblin if necessary. 

"You shouldn't have taken my family!" Bryony tells the goblin as she sinks her blades into it. 

(Rolled with advantage since the gobbo is prone.)

Shortsword: 15 to hit, 9 damage

Dagger: (If Vexed) 21 to hit / (Not Vexed) 13 to hit, 5 damage

Sneak Attack Damage: 8 damage

Jurgen runs (30') ahead, near Quinn, but finds that the last goblin on that side that hasn't fled is dead. He can see the last remaining goblin, prone and facing Bryony and Boona, is still a potential target. (He may attack it this turn, but only with a 35' ranged attack, with disadvantage as it is prone.)

(I'll hold on Boona's turn until the goblin acts.)

Bryony slips past Boona to try to pin that goblin to the floor with her blades, but it is too fast for her (19 Dex! And no Vex.) "I didn't do it!" it shrieks.

(Jurgen may attempt that ranged, disadvantaged attack, if he has one; and Quinn may repost his turn sans attack roll.)

Quinn stops as he watches Fergus mow down the goblin. He scans the room looking for more threats. He looks up, peeks under the tables and then spots the doorway to the east. He rearms Lightbringer and places his ear to the door attempting to hear if there's any movement behind it.

Perception check: 22

The opening to the east is not a door but rather a service window. Quinn gets a good look inside. It's a kitchen. Strips of unidentifiable dried meat and herbs dangle from the ceiling. A squat iron stove stands to the side, its insides glowing with still-smoldering coals. Burlap sacks filled with grain and vegetables are scattered about the floor. A hulking badger burrows its face hungrily into a sack of food. Three goblins - two quite wounded - breathe heavily inside. One of the smaller goblins, watching the window, spots Quinn immediately. It points and shouts a warning to the others. 

In the kitchen, the two smaller goblins dive under the pots and sacks and boxes to hide from Quinn. (Hide: 22, 12). The badger, alarmed by their reaction, does its best to hide as well. (Hide: 16). The big, wounded goblin looks Quinn in the eyes before they go white. 

Synaptic Rend. Everyone (including Jorzu, Laiti, and Hugo): Make a DC 13 Intelligence saving throw. On a failed save, take 13 psychic damage and become incapacitated until the end of the goblin’s next turn. (On a successful save, take half damage only.)

Then, the big goblin, too, hides under a table somewhere. (Hide: 28)

The other big goblin on the floor at Boona's feet is also caught in the blast: DC13 INT Save: 13

The big goblin near Boona, Bryony, and Hugo, stands up, but finds itself trapped. It lashes out at Boona with a blade it conjures from pure thought:

Psychic Blade #1 vs. Boona:17. Hit: 7 psychic damage, and Boona must subtract 2 from the next attack roll or saving throw she makes before the end of the goblin’s next turn. 
Psychic Blade #2 vs. Boona:17. Hit: 14 psychic damage, and Boona must subtract 3 from her next attack roll or saving throw...
Psychic Blade #3 vs. Boona:11. Hit: 16 psychic damage, and Boona must subtract 3 from her next attack roll or saving throw...

Everyone: Make your saves. 
Boona: Make your save, then I'll process that Nat 20 attack (unless you're incapacitated or down.)
Everyone else may act, if not incapacitated or down.
Jurgen: May also get in that ranged, disadvantaged attack, if he has one, just before the blast. Then if not incapacitated or down, he can act with the others.