The Valley of Ends

Gotch will cast detect magic, and identify on the box.

A detect magic gives Gotch glimpses of strange mix of magic coming front he cracks of the box, it seem to alternative between illusion and conjuration but never both at the same time. Identifying the box shows the box itself just a wooden box. 

Salys glances around at the others, "Unless someone has a better idea, I say we just smash it and hope for the best?"

Resfaen will say a silent prayer and then reach into the box grabbing the smaller box and pulling it out.

„Maybe get some magical protection before you try to open it?“ Onyx says while backing away.

Gotch would open the outer box to get a better look at what is inside, so he can identify the item that is magical.

Resfaen reaches into the large box and pulls out the smaller ornate box that been investigated by Salys and Identify as a normal wooden box by Gotch while he can see illusion and conjuration magic emitting from the cracks in the lid. 

Looking back at the group, "So want me to open it? I would not be offended if you left the room before I did." Resfaen states.

(roll a 1d100 when you do open the box)

Salys shrugs, "Here or there, I don't think it will matter. Go ahead and open it and let's see what happens."

Reginald will turn her back to the group and move as far away as she can from them and then open the box.

70

As Resfaen  opens the box and from other side of the attic space, they seen a mass of blackness rush out of box and consume Resfaen's head and soon after, they hear something they never heard before. They hear Resfaen scream in terror before the black mass around her head disspate like mist and Resfaen drops to her knees as she struggles to catch her breath from her screaming.

for Resfaen:

The box drops from lifeless fingers as Resfaen continues to stare straight ahead not blinking, Oh god the darkness consumes all! There is no hope. she thinks and shudders.

Turning back around to her companions, shoulders slumped, "There is nothing to gain from this box as it is empty, just like any hope I might have had in coming here, only death awaits. Lead on friends I will follow behind." With that she slumps against the wall, shallow breathes escaping her pursed lips.

Salys looks suspiciously at the box and his friend, knowing giving up doesn't sound like her. He then orders Bearskr to open the box.

With nothing else of note and Resfaen's apparently shrugging off whatever came from the box, the party starting carefully searching the house room by room level by level but Resfaen lingers away from everyone during the searches. Nothing comes of these searches beside a barren rooms.

The first stepping into the basement is meet with a squishy noises after a few steps in, Looking down to find the ground is covered in a thin patches of something not quite liquid, not quite solid. It doesn't take long to figure out what the source is, a huge pile of slime is in the corner of the open basement. Beisde the huge unmoving pile of slime, there's what seems like a very crudely made table, chair and what looks like books on it in the basement. The entire floor seems to strong sulfur smell to it coming from the pile of slime. 

(I take too long writing out seems)

Bearskr interaction with the box doesn't cause anything to happen. Whatever magical effect that was there had left. 

Onyx will take the now empty box and put it in his bag. „Maybe it can be studied later to give answers what happened to Rasfean. Does anyone of you got something to inspire courage into her?“ The tabaxi asks worried.

Onyx will take the lead downstairs. When they discover the slime, he will shoot an arrow from a distance just to make sure it is dead and collect some sample in to one of his empty vile.  

Onyx collects a sample and takes a few steps away with his vial but look again at the vial where he hears a hissing sound to find the sample he collected is bubbling and disappearing.

Arcana Check Please with advantage and Slight of Hand if you want to collect parts

Between the pile of slime and strong sulfur smell with the huge mass, the party found it's Oblex or rather an Elder Oblex. What the party recalls with ease is anything detached or too far from the ''core' ceases to exist. Finding the core requires some picking of  the brain (arcane check with advantage) to identify but the party is aware of it's existence at least. The Core is only salvable part of the Oblex.

The desk looks like it has some oblex slime covering but for most part intact with some books and scrolls.

What does the party wish to do? 

Gotch moves to the desk to see what books and scrolls are there.