Sidenote; if Guiding Bolt hit. Next person to attack gets Advantage.  So I think whoever posts an attack next since PbP round order is more fluid than normal. So I think its easier to just have whoever hits next after GM Confirms it hit, get the advantage~

The creature parries Daelnar’s attacks with its longsword, sliding in close to deliver a swing of its own.

Longsword @ Daelnar (advantage): Attack: 12 Damage: 8 

It also attempts to rake his flesh with its claws.

Claw @ Daelnar (advantage): Attack: 23 Damage: 7  (if hit, make a Con saving throw.)

Init (bold may act): PCs, undead

Shagar will use her bonus action to cast Ensnaring Strike then take another shot using one of the +1 arrows

Attack: 29 Damage: 10

(if hit the creature must make a DC 11 Str saving throw. on fail the creature is restrained)

(damn)

Stubborn thing just refused to die! Katia tried to take a better aim and made a shot. Then sent the firebolt after the real one:

Crossbow Attack: 26 Damage: 16

Wild Magic: 20 if failed: 83

Attack: Fire Bolt Attack: 7 Damage: 7

Deal at recovers from his missed attack to defend the obvious attack with the long sword, but the swipe of claws catches him on the arm, leaving a shallow cut. The barbarian steps forwards, trying to make room for his companions to get clearer lines at the zombie-like thing, without Daelnar having to deal with further projectiles flying past him. He arcs his glaive with his movement to strike back, before stopping the polearm's motion and shunting the shaft towards the creature's chest to push it back to the wall.

Con Save: 24

Action: Attack: 18 Damage: 7

Bonus Action: Attack: 12 Damage: 8

"I don't know what you all are mumbling about but this interloper needs to be dealt with and fast," Red Chanter intones. "Does it really think it can overpower all of us? Lich, please!"

Vicious mockery - WIS save DC 13 or take 2 psychic damage and have disadvantage on its next attack.
Healing word on Harley for 7 HP

"doubtin its a lich. Too weak and frail." Ol' Malik joins in on the insult.  Tapping his obsidian orb, a soft fire alight within it, "Oh poi " and fire springs beneath the creature.

DC 13 vs  3fire damage on creature. that square is on fire for the forseeable future as per spell

"Always so literal. No appreciation for quality comedy. No respect, no respect!" Red Chanter says in a deep fantasy-New York accent as she adjusts an invisible necktie.

Harley watches the creature and decides that she'll stay far back, throwing her handaxes instead of moving in.

Attack: 13 Damage: 8

Attack 2: 17 Damage: 2

She keeps an eye on its position and tries to tell how injured it is so far.

Katia’s crossbow bolt nearly takes the creature’s head, and Daelnar’s second attack caves in its chest cavity.  It staggers, the red light fading from its eyes, before it collapses in a heap.

On the body you find:

• a longsword
• longbow
• studded leather
• a set of keys

The room from which the creature emerged is a sort of lab.  Six long stone tables are set with steel and glass laboratory equipment, reagents, and bubbling mixtures.  The walls are lined with shelves holding all manner of strange knickknacks and tools. 

The shelves hold spell components, reagents, and laboratory supplies that are far past their prime. However, spending a few minutes searching the shelves can collect enough workable tools and reagents to put together a set of alchemist’s supplies.

The door to the northeast (bottom right) is unlocked.  A cold wind howls through the collapsed east wall of this huge chamber, whose far side is completely submerged under frigid seawater. A dense bed of kelp grows up from the submerged floor, obscuring any sight of what lies below. Broken glass and the remains of shattered tables cover the floor in the dry section of the room.

(Wisdom (Perception) DC 14):

 Shagar notices a stone chest built into the floor and submerged in the water against the far wall.

Perception: 9

Katia Perception 2

"The creature seemed to make that disease. Do not know how but this is what it said." Katia tried to remember the exact words. "No... Not exactly, it said "you came to undo my work" when I asked about the cure. Same thing right?" She was walking along the lab benches but even her common sense was good enough to not touch anything. She was just looking for the golden vials or the "milky" liquid.

"Be cautious, we are not alone in this room" Shagar will point out that there are several giant crabs lurking below the water on the far side of the room. She will also tell about the chest she noticed submerged near them. "I don't know if they are hostile or pets of this other one, but could be the cure is safeguarded in there." She will look to see if the rest of the party is following her train of thought. 

"Argh. That water be a cold thing. Much less the pinchies below.  I dun suppose we got some rope and someone good at lasso or fishin ya?"  Malik laughs a bit pulling out his pockets and showing no rope to speak of.  "I guess some o us check around, some keep an eye on dinner down there.  That said. There stil lbe a room of swords and the blocked room left ya? Mayben we can chip a small hole in the door and take a peeker?"  The Old Man Illuminates his obsidian orb upon his cane. Light shining between his fingers as he grasps hold.  "Mayben could toss light down and dissuade em from bein there?" The old man has ltitle else to offer, until he thinks on a moment.

"If they come out of the water. Maybe they'll have a chat?"  

(GM.  Would we know if theyre "beast"  sort of thing?  Mali khas "Speak with Animals" invocation so he can speak with animals.. I'm uncertain in 5E if Crabs count? haha. and Unsure what if anything Malik would know about it with a -1 to Nature.)

"The rope we have," Katia demonstrated the silk rope that they inherited back in the camp, "but how do you fish with just a rope?" She did not possess such skill and was genuinely  curious.

Not touching any of the unfamiliar lab equipment, Harley makes her way over to look at the water. "Depends what we're trying to fish. If it's hauling out the chest, maybe a hook or anchor with the rope would do the trick. I have a hammer or a crowbar and we could try some creative knots perhaps."

She looks at Malik with a grin, tapping a remorhaz javelin against the ground. "Unless you meant the crabs, in which case any goliath worth her salt would have experience with spear fishing."

"Heh.  They could be tasty.. but lets tryn something different. "  Malik borrows Katia's rope, and throws one end into the water with a kersplash, then quickly reels it in. Waiting a few moments to see if the crabs come out.  Then repeats the proccess if they don't come at first. "Mayben there's something that would wet their appitite ? We got any of that wyrm left?"  the old man murmers at the group.

(Malik is trying to get one to peek its head or part of it out of the water. So he can try to talk to it with Speak with Animals.)

A giant crab, the size of a walrus, clatters up out of the frigid water.

Red Chanter wanders around the laboratory with wonder. She starts a small collection of bits and baubles that look like they might be helpful and stuffs them in her sack. Having absolutely no experience in alchemy, she can only guess as to the intended uses of most of this but, at the very least, someone back in town would probably pay a few gold for it. Sehanine knows that poor pile of bones had no more use for it.

Watching Malik coax out the large creature, Red Chanter backs up a pace and whispers, "Careful...I've heard of the ill temperament these beasties have. They can be quite...crabby."

Shagar is not making any aggressive moves but is tensed ready for action.