(Finished editing) 

Wis save: 16 Dex save: 20

Mrs. Durst is able to dodge much of the angelic blades, taking little damage from them. She is surprised though by the spiritual weapon you conjure, as well as the sacred flames you call down.

Pulling back from you, she moves back to the corner of the chamber. "Leave this place." She orders in her hissing voice. "My husband was a fool, and his bastard son not even useful in the end."

Bernard is barely able to overcome his anger, but something surprises him.

"Bastard son- you mean Walter? Where is he and what have you done to him!" 

He brings the spiritual weapon closer and uses his action to ready another sacred flame. 

"Maybe you should go down the stairs and find out for yourself." She says with a gastly grin.

Disgusted by how corrupted the creature is, he says sharply, "Then may the gods have mercy on your immortal soul."

Spiritual Weapon : Attack: 19 Damage: 12

Sacred Flame  6 or DEX Save 15 

Dex save: 9

The spirit weapon strikes true, but it is the sacred fire that sears into the undead, turning her flesh to crisp and then to ash. With a mocking glare she crumples in on herself, only blackened bones hitting the ground.

We are out of combat now. You can acquire all of the items from the chest now. Please let me know where you go next.

Bernard takes the items and looks morosely at the blacked bones. He doesn’t even dignify Mrs. Durst with a prayer and heads out to the door in the south wall.

As you reach the door, and try to open it, you find your hand is stuck to the door...

Adhesive (Object Form Only). The mimic adheres to anything that touches it. A Huge or smaller creature adhered to the mimic is also grappled by it (escape DC 13). Ability checks made to escape this grapple have disadvantage.

The door then shifts, a mouth forming, and snapping at you...
Bite. Melee Weapon Attack: 24 to hit, reach 5 ft., one target. Hit: 10 piercing damage plus 4 2 acid damage

Mimic initiative: 21
Your initiative: 13

You are up. Your hand is held by the mimic, and you would need to escape the grapple to be able to use it. Escaping the grapple is a full action though.

The mimic door engulfs his arm and Bernard panics. He realizes how close he is to death's door, and his bravery a moment ago fades as all he can think about is escape. 

BA: Cast Sanctuary on self, WIS 15 to harm Bernard 

Action: Attempt to escape grapple Acrobatics: 9

(If the mimic manages to attack Bernard, he'll use his Warding Flare to grant disadvantage) 

Wis save: 15

The mimic is not able to attack you. Back to your turn.

Bernard tries to squirm out of the mimic's grasp.

Action: Attempt to escape grapple Acrobatics: 9

(I don't think he'll be able to get out any time soon, and I doubt he'd able to defeat this mimic) 

n/a

With its inability to attack you, the Mimic seems to pull back, unsure of what to do. "Master?" It speaks in broken common. It does not attack, but it also does not allow you free as of yet.

Your action again.

Bernard answers back, "Yes, I am your master! Please, can you let go of me?" 

Deception: 3

If unsuccessful, he continues trying to break out. 

Acrobatics: 11

"Yes master..." The mimic garbles out in broken common. It releases you and seems to wait for a consiquence for attacking you, quivering a bit. When none come it returns to looking like a door again.

What do you wish to do now? The only place unexplored is the stairs downward. Short rest, or even a long rest, is possible, but might take some planning as to where you would like to do that in this house.