The skeleton is wiped out and the blob looks like it is starting to lose cohesion. It is no longer a squared-off mass.

 The reindeer fly forward to pummel the blobby mass with their hooves.

CON save moon 13

CON save ice 16

Quote from MidnightPlat >>

Dang, I also forgot the rest of my move after the rolls.  Tommary then cunningly disengages back to B to check on the drainskull, addressing it with "what da fu-?"

EDIT: noting the mass healing word was noted on sheet

One of the gems in an eye socket flares! The skull cackles and the party can see a ghostly image of Tommary being pulled from his body! 

Tommary make DC 18 CON save vs soul drain. On a failed save, take necrotic damage equal to half your maximum hp. No damage on success.

Tentacles erupt from the green blob and pull one of the reindeer within the jelly, you can see it struggle and almost hear the cries of panic and pain. A crustacean creature inside the blob also attacks the reindeer.

Everybody go!

Tommary's soul retention plan CON 17

As the last of the soul the thing is able to extract from Tommary the Unworthy exits his breath, Tommary the Perhaps Totally Deserving of That in the Grand Scheme of Things hisses

Suddenly, I'm not half the man I used to be
There's a shadow hanging over me
Oh, yesterday came suddenly

as Dissonant Whispers at the Thing in the Drain, then uses his cunning action to disengage and retreats to the hex to the upper left of Ilyra's hex.  

11 psychic damage and retreats or a WIS 15 save to take have damage and no retreat.

36 points necrotic damage noted.

Sound Effect:

WIS save 23

*Legendary Resistance used*

“Tom’ry! Are you okay?!?” Toots shouts as she aims the Diamond affixed to her lute directly at the slime monster and riffs. An orb of magical fire flies directly at the slime monster as she casts chromatic orb cranked to 5th-level- (Attack: 20 Damage: 32 the d6 is necrotic). She then whirls her lute and brings her spiritual weapon to bear against it again- (Attack: 16 Damage: 11 force and the d6 is necrotic damage). “Maybe Ily’s right?!? Maybe we should make like shepherds and get the flock outta here?!?”

""I am definitely not OK! I am half expecting Rodan to appear in his Morpheus avatar and ask me "How did I beat you?""

EDIT: corrected the line

"I think Ilyara and Toots are right."  Elyona says.  She'll ask (not order) the remaining reindeer to attack the blob.  

If any of the party ends up within 5 feet of her and is then attacked, she will use her protection fighting style to impose disadvantage on the attack.

Moonbeam damage: 11 DC 16 CON Save for 1/2 damage

CON save moon 24

The blob is looking much more bulbous and no longer has sharp corners, definitely losing shape and becoming more wobbly.

Ilyara go!

OOC: I begin a week's vacation today, and will be on the road much of the day, so I'm not likely to be able to check in today.  I think I should be able to much of the rest of the week, but vacation activities will take priority.

Quote from ArwensDaughter >>

OOC: I begin a week's vacation today, and will be on the road much of the day, so I'm not likely to be able to check in today.  I think I should be able to much of the rest of the week, but vacation activities will take priority.

 OOC: Ooh! Have Fun!!

OOC: Should be three patches of flame, methinks.  One additional one right at the source of the acid flow.

IC:
Ilyara growled under her breath, picking up on the new threat as Tommary got himself zotzed by something in the sink.  The whole battle was slipping out of control, they were barely hanging on.  The acid was a problem, but it wasn't the main problem just at this moment.  Focusing, she flicked a claw against Rilia's pommel and sounded her bells again, targeting the flagging jelly mass with more necrotic energy.  At the same time she commanded her blade to strike again, hoping to pile on the damage and end the major threat before things got worse.

{Wis 15 save against 10 necrotic damage}
{Spirit Blade attack roll: Attack: 14 Damage: 7}

OOC: Wysp is dropping hints that the slime monster isn’t long for this world. Should we try to stick it out in this fight, or retreat, regroup, and either bypass it or try again?