(Rolling C3 CON save now.) 3

C1 crumbles without a noise on the first swing. (These are your run-of-the-mill cultists, so very squishy.) The bright flash of radiant energy lights up the chamber. Annoyed at how easy that was, Jorin's second swing hits C2, who also goes down.

Quillary gives C4 a hard whack on the noggin, but the cultist is still awake (though very woozy). C3 was not expecting this, but is reaching for the scimitar.

Hildigrim is up. (Then the grells, and C3 &C4.)

(OOC: I don't remember if there was a decision about non-lethal or not. You get to choose after the hit and damage rolls. These guys are wearing full cult outfits, including the creepy outer god symbol. As long as you find evidence of evil sacrifices, there shouldn't be too much trouble with the Greenfast authorities.)

(Oh, Quillary is happy to let them experience passing through the veil for themselves. She’s not pulling her hits.)

Staying on the stairs, Hildigrim loads an arrow and watches as Quillary and Jorin rush forward. As soon as he knows who they're going after, the halfling lets his arrow go at one of the other two.

Attack: 24 Damage: 7

He then gives Drusk some advice on how to attack the beaked brain things if he chooses to do that.

(Jorin took the lack of reply to post #5467 as implicit agreement about bloodshed lol)

(A little ret-con of the situation.)

Jorin rushes forward on the west side to take the cultists in the back. Not very sporting, but people that support family sacrifices don't deserve a fair shot.

The two to the east are startled at their buddies being hacked apart without any noise.
The C4 cultist (who is not a block of explosives) turns towards the wall opening on the east wall, cups his hand to his mouth to shout something... and nothing comes out. His surprise is momentary, as Hildigrim's arrow (even without sneak damage) goes through his open mouth.
The remaining C3 cultist is starting to draw his scimitar when Quillary emerges from the dim lighting, her spore cloud obscuring her approach until the last moment. The cultist is dizzy after being hit in the head with the club, and then he is engulfed by a wave of spores. You can't see what the spores are doing, but the cultist quickly falls over and stops moving.

The 2 grells are able to feel Quillary and Jorin run to the south, with the air movement and any faint static electricity, so they both float to the squares 10' south of the braziers at the entrance. That puts them 5' north of Jorin and Quillary. They attack with tentacles and their beak. (If the tentacles hit, the target is grappled and restrained.)

• Tentacle Attack vs Jorin: 12 Damage: 7  (miss)
• Tentacle Attack vs Quillary: 24 Damage: 16  (ouch)

• Beak Attack vs Jorin: 10 Damage: 7  (miss)
• Beak Attack vs Quillary with advantage: 12 Damage: 4  (miss)

Quillary rolls a CON save vs. DC 11 or be poisoned and paralyzed.
She is grappled (escape DC 15) and restrained by the grell's tentacle.

Drusk already went (cast Silence spell).

New round...
Hildigrim is up, then Jorin and Quillary.
Then the 2 grells. (The 4 cultists are dead.) Then Drusk at the end.

(Ouch. I'll also roll a Con Save for her concentration, I assume I should roll that separately from the poisoned condition save. Is any of the damage poison damage, I ask because she is resistant to that.)

Con Save #1 to avoid being poisoned and paralyzed (she has advantage for saves vs poisoned) vs DC 11: 14
Con Save #2 to retain her concentration on PWT, vs DC of 10: 12

Still grappled, regardless of what happens above.

(The grell's damage is all piercing from the barbed tentacle. The poison is a paralytic only.)

Hildigrim draws another arrow and aims for the creature binding Quillary. Volo launches off of the halfling's shoulder and does a flyby to help distract it.

Attack: 19 Damage: 8

Sneak attack: 8

He then points out something to Jorin about the creatures that should make it easier for him to hit it.

STUPID board!

If Jorin is able hit the same Grell that has Quillary grappled, he'll attack that one.  Otherwise, the other grell.

• Action:  Battleaxe!
  • Attack w/ Adv from Hildigrim: 24 Damage: 12
  • Attack: 25 Damage: 13
• Bonus Action: Moonblade!
  • Attack: 21 Damage: 11
• +7 radiant to the first attack that hits

(I'm waiting to see if either of these attacks free Quillary before deciding whether to try to escape the grapple... but while we're here, if a M creature that is grappled wild shapes into a L creature, what happens?)

For Hildigrim, I noticed that DirtyDogP has been posting every other day. No problem with that, except for those pesky "Dice rolls not yet available for this section".
I'll wait a few hours to see if those are fixed (I usually edit my post to add extra spaces before or after any roll commands), but otherwise will re-roll Hildigrim's attacks.

For Jorin, that brings up an issue about AoO without a clear cut answer.
The grell's attacks have a reach of 5' (beak) and 10' (tentacles). He can attack the grell grappling Quillary, but that means moving 5' from the other grell. He is still within reach of the tentacles, but he has moved out of the beak range... I'm going to give it an AoO with the beak. I'm guessing that he doesn't mind the risk of minor damage, in order to free Quillary from being attacked with advantage.

For Quillary, shape-changing to a Large size means the grell can still grapple (PHB, allows up to one size larger), but the restrained condition goes away (MM, medium or smaller only).
But that might be moot. If Hildigrim hits with at least average damage, the grell will go down. (Jorin only missing with a "1" really racks up the damage.)

Oh that is an interesting question, moving out of reach from attack but not the other.  I think I'd run it the same way you have, so Jorin is happy to be beaked

Beak Attack of Op: 9 Damage: 8

Rolling for Hildigrim's bow Attack: 28 Damage: 38

Jorin fends off the tentacles, but G1 gets a bite with its beak. Jorin takes 4 damage (after rage reduction).

Hildigrim's arrow hits, but the damage is below average. However, it wounds G2 enough that Jorin's 3 hits are able to take down the grell.

(Quillary is no longer grappled or restrained. The other grell is 10' away to the NW.)

Quillary, shrugging off the tentacles of the dead grell, spins and faces the last one. Still smarting from the first one's attack, she backs away from it and points her club, spores swirling along it and to the creature, the cloud intimating a gray ghostly hand grasping for it.

Move: turn to face the grell, then back away ten feet
Action: cast Chill Touch on grell. 24 to hit, for 13 necrotic damage
Bonus Action: Nope
Reaction: If the grell moves within 10' of Quillary, Con Save vs DC 16 or take 5 necrotic from Halo of Spores

edit: ack, I messed up, subtract 5 from that damage, so just 9.

(OOC: I was going to have the grell do an attack of opportunity against Quillary, since the tentacles have 10' reach. But then I remembered it used its Reaction to bite Jorin.)

Quillary cannot cast Chill Touch, which has a Verbal component. (She is within the Silence zone.)
Since she has plenty of movement, and she knows the grell cannot use an AoO, she will instead do the following.
She moves 5' forward, whacks the brain piñata with the shillelagh (19 to-hit, does 7 magic damage), then moves 15' back to the eastern wall.

The grell moves forward, but Jorin is in the way. Tentacle and beak attacks against the bitten barbarian. ("Tis but a scratch.")

• Tentacle Attack: 14 Damage: 5  (miss)
• Beak Attack: 5 Damage: 4  (miss)

Drusk moves south and tries to bring a little Joybringer to this aberration.

• Mace Attack: 14 Damage: 7  (hits)

New round... The map image above is the current situation. The blue area is the Silence zone.
Hildigrim is up, then Jorin and Quillary. (Then the remaining grell, if it is still alive.)

(Totes cool with that resolution, I’d obvs forgotten about Silence)

Stupid board ate my rolls. They were there, as I'm sure you suspected.

Feeling calm and sure of a victorious outcome, Hildigrim decides to save his third arrow. He steps down the stairs and up to the grell, drawing his rapier as he does so. Marveling as he enters the sphere of silence, but concentrating to keep it from distracting him, he thrusts the pointy end of his weapon at the brain thing.

Attack: 13 Damage: 7

Sneak attack: 14

Hildigrim is able to stab the un-armored brain-like monster for 21 damage.
(It has taken 35 damage in total, hurting but still plenty of health.)

Jorin and Quillary are up.

(Turns out *all* of Quillary's spells, save one defensive reaction spell, have verbal components. Huh.)

Quillary grumbles as she thinks a moment, then dives in to the fight, charging straight ahead to get to the grell and strike it with her club.

Move: forward 10' to just below Jorin
Action: swing magic club at grell. 10 to hit, for 11 magical bludgeoning damage
Bonus Action: none
Reaction: when the grell starts its turn, Con Save vs DC 16 or take 3 necrotic from Halo of Spores

Quillary hits for 8 more damage.
She suspects that the cost to clean off the grell—brains will be more expensive than buying a new club or finding a suitable stout tree branch.

(Jorin is up. Unless he rolls 3 natural ones on his turn, this grell is a goner.)