The Coast Way
Xzar squints into the darkness and remarks quietly, "I wanted darkvision like the elves, but 'tis more than just taking their eyes..."
Imoen, who has been chatting happily with the wizard up until this point, gives him a sidelong look and chuckles awkwardly, unsure of exactly what the man means. Before she can ask, however, the screeching begins.
"blarkblarkblarkblark SKREEEEEEEEGLURKLGLURKL!!!"
Runeson recognizes the mad call of gibberlings, as do Xzar and Montaron, who immediately draw weapons. The noise seems to come from all around them, and Runeson can't help but remember the last time he fought the strange monsters.
Unwilling to face gibberlings in such darkness, Xzar conjures his dancing skull-lights, which bathe the immediate scenery green. Dozens of eyes peer back at the party from the darkness all around, and then the gibberlings attack!
As for how they enemies are grouped, they share a hit point total. So if you happen to do 15 damage to a group, you kill all 3 gibberlings in that group (each gibberling has 5 hp). Make sense? Feel free to ask questions in the Discord!
I FORGOT TO ADD: Attack rolls against these guys ALL HAVE ADVANTAGE. Cuz reasons.

Stella's frightened eyes soon flare a fierce orange. They were not going to lose any more.
She knocks an arrow and blows an icy druidic word onto it. The arrow becomes encased in frost, then she draws and sends it into one of the groups of approaching creatures before it explodes into a sphere of icy shards.
(Stella casts Ice Knife. North Front takes 2 damage and two of them must succeed on DEX saves or each take 11 damage, or however the mobs work.)
AC: 13
Middle
Rolls
NO. BAD. Ice Knife vs North Front (Adv) - (1d20+5, 1d20+5)
1d20+5 : (3) + 5 = 8
1d20+5 : (7) + 5 = 12
Attack Damage - (1d10)
(2) = 2
AoE Damage - (2d6)
(65) = 11
Stella's arrow is far more impressive, and Wirrow gives it an appreciative glance and smile.
(Wirrow casts Looming Shadow. East Front takes 12 piercing damage, and one of them takes an additional 1d10 psychic damage on its next turn if it takes any hostile action towards Aiwe.)
HP: 20/20
AC: 14
Middle
Rolls
Longbow vs East Front (Adv) - (1d20+7, 1d20+7)
1d20+7 : (10) + 7 = 17
1d20+7 : (9) + 7 = 16
Damage (Longbow, Favored Foe) - (1d8+3, 1d4)
1d8+3 : (8) + 3 = 11
1d4 : (1) = 1
Without Ossein's help, the Zombie Archer plucks a crooked arrow from the air, looses it, and blasts the group of chitterlings apart.
"Lucky Shot, you cheated, it doesn't count."
Group to the south takes 15 damage
AC: 13? I think
HP: ∞
Loc: middle
Rolls
Arrow'd - (1d20+5)
(20) + 5 = 25
Damage with crit - (1d6+9)
(6) + 9 = 15
He slashes out at the gibberlings. The tip slashes out and hits first one gibberling, and then another, with almost no effort.
(10 damage to West)
AC 14
HP 17/17
West, front
Rolls
Rapier attack! - (1d20+5)
(12) + 5 = 17
Again, bc advantage - (1d20+5)
(15) + 5 = 20
Damage - (1d8+3)
(1) + 3 = 4
Sneak attack! - (1d6)
(6) = 6
Whip deals 9 damage along with any damage Stella does.
HP 19
AC 17
Rolls
Whip vs North - (1d20+6)
(9) + 6 = 15
W Adv - (1d20+6)
(20) + 6 = 26
whip crit damage - (1d6+6)
(3) + 6 = 9
Be careful! They will try to separate and drag us away!" I yell, thinking of the poor guards from last time.
I swing at the closest gibberling within range."Justice smite you!"
6 damage to western gibberlings
AC: 18
Health: 20/20
Front: West
Rolls
Attack western gibberlings - (1d20+5)
(13) + 5 = 18
Advantage- western gibberlings attack - (1d20+5)
(17) + 5 = 22
Damage - western gibberlings - (1d8+3)
(3) + 3 = 6
16 dmg to East group, killing all three there.
Rolls
Shortsword vs east group (adv) - (1d20+7, 1d20+7)
1d20+7 : (13) + 7 = 20
1d20+7 : (3) + 7 = 10
dmg to east (piercing, sneak attack) - (1d6+4, 4d6)
1d6+4 : (4) + 4 = 8
4d6 : (1232) = 8
Dmg is as follows…
Sheemish takes 14
Montaron takes 16
Aiwe expends her thingy and is at 1 hp
Rift takes 10
Fortunately, these beasties also fall easily. In just seconds the first wave of enemies are cut down, though more feral screams and insane chatterings signal the arrival of the rest of the gibberlings. What's worse, a handful of them are climbing up nearby trees (Climbing Groups 1 and 2).
Rolls
North group vs Sheemish (swarm, adv) - (1d20+4, 1d20+4)
1d20+4 : (20) + 4 = 24
1d20+4 : (11) + 4 = 15
attacks vs Sheemish (4, adv) - (2d20+4, 2d20+4, 2d20+4, 2d20+4)
2d20+4 : (1216) + 4 = 32
2d20+4 : (22) + 4 = 8
2d20+4 : (1017) + 4 = 31
2d20+4 : (1412) + 4 = 30
dmg to Sheemish (piercing) - (3d4+6)
(413) + 6 = 14
East group vs Montaron (swarm, adv) - (1d20+4, 1d20+4)
1d20+4 : (20) + 4 = 24
1d20+4 : (3) + 4 = 7
Attacks vs Montaron (4, adv) - (2d20+4, 2d20+4, 2d20+4, 2d20+4)
2d20+4 : (511) + 4 = 20
2d20+4 : (717) + 4 = 28
2d20+4 : (139) + 4 = 26
2d20+4 : (616) + 4 = 26
dmg to Montaron - (4d4+8)
(2114) + 8 = 16
South group vs Aiwe (swarm, adv) - (1d20+4, 1d20+4)
1d20+4 : (16) + 4 = 20
1d20+4 : (4) + 4 = 8
Attacks vs Aiwe (4, adv) - (2d20+4, 2d20+4, 2d20+4, 2d20+4)
2d20+4 : (1420) + 4 = 38
2d20+4 : (1119) + 4 = 34
2d20+4 : (314) + 4 = 21
2d20+4 : (1914) + 4 = 37
dmg to Aiwe - (4d4+12)
(3324) + 12 = 24
West group vs runeson (swarm, adv) - (1d20+4, 1d20+4)
1d20+4 : (5) + 4 = 9
1d20+4 : (12) + 4 = 16
West group vs Rift (swarm, adv) - (1d20+4, 1d20+4)
1d20+4 : (6) + 4 = 10
1d20+4 : (17) + 4 = 21
Attacks vs Rift (4 attacks, adv) - (2d20+4, 2d20+4, 2d20+4, 2d20+4)
2d20+4 : (184) + 4 = 26
2d20+4 : (96) + 4 = 19
2d20+4 : (517) + 4 = 26
2d20+4 : (73) + 4 = 14
dmg to Rift - (2d4+4)
(24) + 4 = 10
North group dex saves vs ice knife (3 saves) - (3d20+2)
(41110) + 2 = 27
As a clarification, still adv on all attacks against these moops!
Good news is, this should be the last of them.

10 dmg to the climbing group 1
Middle
Rolls
Imoen vs climbing group 1 - (1d20+5, 1d20+5)
1d20+5 : (6) + 5 = 11
1d20+5 : (12) + 5 = 17
dmg to climbing group 1 (sneak attack) - (2d6+3)
(25) + 3 = 10
21 dmg to East group
East
Rolls
Montaron vs East (adv) - (1d20+7, 1d20+7)
1d20+7 : (13) + 7 = 20
1d20+7 : (8) + 7 = 15
dmg to east - (2d6+4)
(43) + 4 = 11
REAL damage roll (piercing, sneak attack) - (1d6+4, 4d6)
1d6+4 : (1) + 4 = 5
4d6 : (5335) = 16
Hopefully
dex 14 save Vs catapult or death
hp 5
Ac 17
Rolls
Decapitated catipult - (3d8)
(584) = 17
Dex save - (1d20+2)
(17) + 2 = 19
Dex 14 save next group - (1d20+2)
(12) + 2 = 14
Maybe?!?! - (1d20+2)
(19) + 2 = 21
10 damage to south side.
AC: 13
HP: ∞
Loc: middle
Rolls
Arrow'd advantage - (1d20+5, 1d20+5)
1d20+5 : (19) + 5 = 24
1d20+5 : (1) + 5 = 6
Damage - (1d6+4)
(6) + 4 = 10
He swings again and watches several of the monsters fall. "Take that, you nasty things!"
(13 damage to West side)
AC 14
HP 7/17
Front, west side
Rolls
Rapier attack again - (1d20+5)
(3) + 5 = 8
Advantage - (1d20+5)
(19) + 5 = 24
Rapier damage - (1d8+3)
(4) + 3 = 7
Sneak attack - (1d6)
(5) = 5
"With that great blow her vision fades
She sinks beneath the waves
Is this where the story ends?"
"KIO-RAAAAA!" Aiwë's shout echoes far more than it did in the Hearth, her voice ripping into the gibberlings and blowing them away. She draws her sword as the resonance works through her, filling her with strength.
"This will not be her grave!"
Aiwë casts Thunderwave on then North side, destroying the gibberlings. She then casts Cure Wounds on herself and gains 9 hp.
HP: 10
AC: 14
Rolls
Cure wounds on self - (1d8+3)
(6) + 3 = 9
Thunderwave saves - (1d20, 1d20, 1d20)
1d20 : (13) = 13
1d20 : (8) = 8
1d20 : (13) = 13
Thunderwave damage - (2d8)
(85) = 13