Spike:

Sensing weakness, Spike redoubles his efforts and attacks with reckless abandon!

Reckless attack:  Attack: 25 Damage: 6

Reckless attack:  Attack: 25 Damage: 8

Bonus Grapple:   11

(Attacks have advantage against Spike this turn)

Seeing her arrow do no damage Kiza moves into melee range and attacks with her rapier casting booming blade wreathing the rapier in thunderous energy.

Rapier attack

Attack: 9 Damage: 7

Thunder damage

8

Thunder damage if the creature moves 5 ft

9

Bonus action using Cunning action to disengage and move back out of melee range 20ft.

End of Turn

Both of Spike's attacks connect to the creature.

The creature crumbles to the ground. Parts of it scatter as it hits the floor and a couple slide across the room.

Combat has ended, for now.
Actions?

Kiza keeps her rapier out in case something else decides to animate and attack then. "Good job everyone, we still live. Now lets try walking around the sarcaphagus and any other magical item in here." 

Kiza will head to the other door skirting the perimeter of the room giving the sarcophagus a wide birth. Once standing before the door she checks it for traps

Investigation Check

18

Enoch looked at the fallen construct and simply shook his head. "I would have loved to have gotten some answers from that thing, but... it was just a 'thing.' And probably poorly instructed at that. Ah well."

Watching Kiza, the paladin similarly moved further from the sarcophagus as she began checking for traps.

Spike:

Moving back to the southern door, Spike waits for the others to finish their investigation.  "Do you need me to open up the sarcophagus?  We may have to fight whomever or whatever is inside."

"I would think that would be a bad idea as whoever Istaris is my come out to attack us. I rather do what we can to not provoke another attack" says Kiza to Spike. 

Essendrum waves dismissively toward the sarcophagus. “I doubt either the one-eyed orc or the wizard’s spellbook are inside and those are what I seek.  I’ll admit I’d love to open it and find a staff of power, but I think it would be wiser to search the halls of the upright first.”

The paladin looked between his companions, then back to Spike and shrugged. "Essendrum's right; the missing contact is our priority." He smiled. "I'm sure if he wants to come after us, Istaris will be able to leave his resting place." Although he'd meant it as a light-hearted joke, even Enoch seemed a bit surprised at how dour he'd sounded about it.

Essendrum nods.  “Well said. The dead do not seem to be resting easily of late.  I’m sure more of them will find us soon enough.”

The party, avoiding the sarcophagus and the remaining statues, make their way to the southern doors.
The doors are oak with brass fixtures and have cavings of the same you have seen in the octagonal/diamond-shaped room. 
It is unlocked and after a quick check, no traps are found.
The door opens to a 15 ft. by 30 ft. room. 
The floor is made of some sort of emerald-colored stone and is covered in a thin layer of dust.
It is easy enough the see the drag marks made across the room to another door along the south wall.
it is set slightly ajar. 
This door opens to a very dark hallway that leads south. 
Cautiously the party makes its way down this hall, some 70 ft. long. 
From here it turns to the east. 
This branch leads another 100 ft. and comes to an intersection.
You can continue going east or, take a hall that leads south. 
Which way does the party go?

DM:
Let me know if there is anything else the folks wish to do while traveling this hallway.

Spike:

Keeping an eye out for traps, especially those that might involve stonework, Spike tires to follow the drag marks as best he can.  When they get to the intersection, he follows the trail if he can.

Perception for traps:  18

Survival for tracks:  8

Kiza keeps quite as she travels down the hall trying to follow the drag marks. She keeps her eyes peeled for signs of danger or anything of note. 

Perception

7

Survival

4

Essendrum investigates the emerald stone.  What type of stone it might be interests him, but he is also intrigued by the layer of dust, since a body seems to have been dragged to this spot and so should have cleared some dust.

Investigation:  10

After looking over the emerald stone, Essendrum gathers that it isn't native to any place he has seen or heard of. It appears to be stone but further investigation would take access to an Alchemy Lab and time. It does seem odd that the drag marks in the dust are only drag marks.

The party comes to the intersection. This is where the trail in the dust stops. The floor appears to be very clean, possibly from use. 

Actions?

"Let me send Venti down the southern passage to scout out for us and we can check what is to see where does this corridor end" says Kiza as scoops up Venti the bat and sends it flying down the southern passage. She then continues onward keeping her peepers peeled. 

Perception 

6

"That's a good idea," nodded Enoch. He waited to see if the familiar returned any bad news.

Essendrum nods absentmindedly as well, mainly concentrating on trying to break off a chip of the mysterious stone for later study.

Kiza

Essendrum pounds on the stone floor, trying to chip it.
Strength Roll, please.

The noise from his efforts however echoes eerily throughout the room and down the halls, both ways.