Round 1 Summary
Chaos.
As horrific powers are unleashed, the Hand continues to tremble.
The larva mage reacts first. With each of Vincent's blows, many grubs and worms flake to the ground, crushed. It whirls on the strange swordsman, only to find him vanished. Chittering incoherently, it raises its staff high and issues a magical blast that zaps both Larrel and the slimy whale (Larrel takes 9, whale takes 8).
The whale hefts its bulk up and rolls over to gaze about with one watery eye. Being out of its usual element and seeing that the most threatening foes will almost certainly be immune to its usual charms, the creature does the logical thing and goes berserk. Tentacles and tail fin lash out in every possible direction... resulting in Gelarith being seized and splattered in frighteningly quick succession.
Focusing primarily on speed, the party twists and dodges through the fray. Most of them are fortunate to get out unscathed, but Alalla and Zenithral each take a hit from a whale tentacle. Alalla shrugs off the hit, but Zenithral begins to feel queasy... (Al takes 11, Zen takes 9 and is diseased)
An elvish curse from an age long gone leaves Larrel's withered lips as the party runs. He reaches out with a skeletal hand to seize Ug and sap away his strength, but Ug manages to pull away from the undead chill and refuses to succumb to its paralyzing touch (After resistance, Ug takes 6 cold damage and is not paralyzed - WHEW).
Then Larrel is forced to confront the other threats in the room. He turns and throws himself into a powerful spell of mass banishment, then claps his hands together in an impressive demonstration of abjuration. For a moment, there is silence as the other three monsters wink out of existence...
Then the archmage turns to cast a single fiery bolt at Ug's fleeing form. The spell hits Ug squarely, but instead of wreathing the goliath in biting flames, there is a flash of white light from Zenithral as the half-elf magically transfers the pain to himself (Zen takes 18 fire damage on Ug's behalf - WHEW).
Larrel lets out a scream of rage and moves to pursue the party, but an awful ripping sound emanates from behind him. "No... NO!" Incredibly, impossibly, the three strange creatures return from their planar jaunt, and once more the room is full of twisted, misshapen monsters (Whale, Larva, and Forgotten each expend a use of Legendary Resistance to avoid Larrel's Banishment spell).
The larva mage stamps the floor with its staff and releases a swarm of biting insects that cover the others, leaving gaping sores and infected wounds, though this tactic seems less effective against Larrel's undead form (Forgotten and whale take 35 necrotic damage, Larrel takes 17).
The floating mass of fat vomit opens its mouth wide and lets out a wave of bile that covers the whale (Whale takes 31 acid damage), then drops its bulk atop the larva mage, scattering its form into thousands of skittering bugs. Then the gross creature turns on Larrel. It speaks a single awful word, and the archmage grasps his head in agony (Larrel expends one use of Legendary Resistance to avoid Feeblemind).
Vincent reappears alongside the companions just as they reach the stairs. The last thing the party sees before going down is Larrel desperately beginning another spell.
Rolls
Larva Mage vs Slimy Whale, Larrel, Forgotten One - (1d20+8, 1d20+8, 1d20+8)
1d20+8 : (18) + 8 = 26
1d20+8 : (19) + 8 = 27
1d20+8 : (3) + 8 = 11
Dmg to Whale, Larrel - (1d10+3, 1d10+3)
1d10+3 : (6) + 3 = 9
1d10+3 : (5) + 3 = 8
Whale attack 1 (random target, attack roll) - (1d10, 1d20+9)
1d10 : (8) = 8
1d20+9 : (16) + 9 = 25
Whale attack 2 (random target, attack roll) - (1d10, 1d20+9)
1d10 : (1) = 1
1d20+9 : (16) + 9 = 25
Whale attack 3 (random target, attack roll) - (1d10, 1d20+9)
1d10 : (5) = 5
1d20+9 : (6) + 9 = 15
Whale attack 4 (random target, attack roll) - (1d10, 1d20+9)
1d10 : (10) = 10
1d20+9 : (18) + 9 = 27
Whale attack 5 (random target, attack roll) - (1d10, 1d20+9)
1d10 : (8) = 8
1d20+9 : (8) + 9 = 17
Whale attack 6 (random target, attack roll) - (1d10, 1d20+9)
1d10 : (4) = 4
1d20+9 : (12) + 9 = 21
Larrel opp vs Ug - (1d20+12)
(6) + 12 = 18
Cold dmg to Ug - (3d6)
(661) = 13
Ug Con save DC 18 - (1d20+7)
(20) + 7 = 27
Dmg to Al - (2d6+5)
(15) + 5 = 11
Al DC 14 Con save - (1d20+9)
(17) + 9 = 26
Dmg to Zen - (2d6+5)
(22) + 5 = 9
Zen con save DC 14 - (1d20+5)
(2) + 5 = 7
Dmg to Larva mage - (3d6+5)
(323) + 5 = 13
Dmg to gelarith - (5d6+10)
(61541) + 10 = 27
Gelarith Con save - (1d20+1)
(9) + 1 = 10
Larrel vs Ug - (1d20+12)
(5) + 12 = 17
Fire dmg to Ug (rerouted to Zen) - (4d10)
(4536) = 18
Acid dmg to whale - (10d6)
(3234415252) = 31
Erevain vs Whale - (1d20+8)
(11) + 8 = 19
Fire dmg to whale - (3d10)
(388) = 19
Dmg to larva mage - (2d6)
(35) = 8
Circle of death damage - (8d6)
(52654535) = 35
