The Fungus Origin

This is an obvious place of natural worship. The trees are neatly pruned, and the grass is well-tended. Among the trees are druid symbols (Druids welcome, others... meh). A carefully placed line of bluish stones set a path leading to a rock cairn where flowers, nuts, berries and garlands of leaves are placed. A small path leads beyond the shrine to a low-roofed cabin under the cover of great oaks. A call will bring forth the druid Jaroo the Ashstaff. All comers to the Grove are expected to make an offering - then and there, and the druid will state this. If the visitors are not druidical, they are expected to give several gold pieces to Jaroo as donations towards the needy of Hommlet. The druid will listen to requests for assistance from those who contribute.
Jaroo the Ashstaff is an Elderly Half-elf with a crotchety demeanor. He misses his old friend, Turrim the Wizard, and is worried about his disappearance. They have a cute, antagonizing relationship that has always bordered on romantic love. He is even crankier now that Turrim is gone. He elected to stay behind in Hommlet as the 'old guard' so that Ottis, Raman, and Drogyn the Battlebrand could search for Turrim. He is originally from the druids of The Gnarly Wood, but has been in Hommlet for too many years to count. as an old man he walks a bit hunched in his green robes. He carries a staff that blossoms at the top like an ash tree. The leaves looks young and green, just like the spring leaves in the grove.
He will ask for the others to make a donation to the grove. If asked he will talk of his history. Being from the Gnarly Wood druid circle on the south border of Kaan. He left as Kaan become more hostile to Elves. He did some adventuring with Turrim, Ottis, and Drogyn in his youth, before they all settled in Hommlet. 
He will assist the others with any questions, if they made a donation. Can also cast Mass Cure Wounds or Greater Restoration.
He will offer to help Hope, but will require her participation. He calls down a bird from the grove, and speaks with it softly. The bird flies off. He tells the group to get comfortable in the grove, he will return. He heads to his cabin.
A few minutes later he returns, carrying a tray with several items. He motions for Hope to sit in the grass. He sits across from her, setting the tray down between them. On the tray he has a waterskin, a bowl, and a small knife. He asks for the sample. He cuts a very small amount of the fungus and places it the bowl. He pours some water from the skin, into the bowl. He picks up the bowl with one hand and creates a small flame in the other. He applies the flame to the water and it begins to steam. Once its sufficiently hot he sets the bowl on the tray and allows it to steep. 
He explains, "We will ingest the tea and meditate. I do not believe this to be a natural growth, we need to locate the place from whence it came." As he's speaking Cleric Calmet arrives, "I got your message Jaroo. I am ready". Jaroo nods, picks up the bowl and take a healthy gulp. He holds it out, gesturing for Hope to take it.
If Hope drinks it... Jaroo bows his head in meditation and in just a few moments, Hope and Jaroo fall over... dead.
If Hope doesn't drink, Jaroo becomes gets upset motioning to Calmet. Calmet waves his hands, speaking a prayer and a light envelops Jaroo. He stands, berating the group and Hope, casting them from the Grove. 
Pause the main group, take Hope aside... You awaken in a fog. As the moments pass the world around you begins to refocus, but it's slow. You begin to make out the shapes of the trees of the grove, but they are leafless. The sky is dark and the grass under your feet is practically without color. In fact, it looks like the color has been sucked from the entire world... only the slightest amount remains. You look around and see Jaroo through the lifting fog. 
"I believe we're in the Shadowfell, a realm of darkness and decay." He motions for you to follow him as he walks closer to one of his trees. He points out a strange gray growth on the tree, it looks like your mold, without color. "This is not good, my dear." He begins to inspect it closer. "I need a minute to study this."
Perception check:
DC10 - Hear some skittering in the fog around you. It's gone by the time you can turn your head. It attacks, surprise! DC15 - You see a shadow in the fog and hear the skittering, but it runs off, then attacks (get 20 initiative) DC20 - You make out the shape of a spider-like creature in the fog, it comes right for you. 
Jaroo, "Buy me some time."

Nightcreeper

Medium undead monstrosity, neutral evil

Armor Class 14

Hit Points 33

Speed 40ft Fly: 40ft Climb: 40ft

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STR

14 +2

DEX

16 +3

CON

12 +1

INT

2 -4

WIS

11 0

CHA

4 -3

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Damage Vulnerabilities Radiant

Damage Resistances Necrotic

Senses blindsight (30ft), darkvision (60ft), PP 12

Challenge 1/2 (100xp)

Spider Climb: The nightcreeper can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.
Web Sense: While in contact with web, the nightcreeper knows the exact location of any other creature in contract with the same web.
Web Walker: The nightcreeper ignores movement restrictions caused by webbing.

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Actions

Bite: Melee Weapon Attack: +5 to hit, reach 5ft, one creature. Hit: 1d8+3 piercing damage and the target must make a DC 11 CON save, taking 2d8 necrotic damage on a failed save, none on a successful one. The nightcreeper gains the necrotic damage back in temporary Hit Points.
Web (Recharge 5-6): Ranged Weapon Attack: +5 to hit, range 30/60, one creature. Hit: The target is restrained by webbing. As an action, the restrained target can make a DC 14 STR check, bursting the webbing on a success. The webbing can also be attacked and destroyed (AC 10, HP 5, vulnerable fire, immune bludgeoning, poison & psychic).

Black spider-like monster with a head and wings similar to a bat.

Shadowfell

Jaroo finishes just when the battle ends, unless he needs to help. "Come, I want to see the sky." Jaroo turns and walks to the exit of his grove. As you exit you can just make out some of the other buildings of Hommlet. Some look burned, others look like they rotted away. They are all in disrepair unlike anything you've seen in the realm of man. You look up and the sky is a dark, not quite black color. There are no stars, but just a solitary moon in the sky. It is a sickly green color, and even though it isn't actually vibrant of color, it is the most color you have seen thus far in this realm.  A low rumble fills the air. You feel the ground shake below your feet in a steady rhythm. About 50ft away you see two creatures break through the ground, they emit a eerie scream from their five petal face filled with teeth, Demogorgins. "We must go", he moves faster than you've seen, making his way back into the grove. As you return to where you appeared you can feel a tug at the very center of yourself. Not your body, your being. You see Jaroo stop at one of the trees, grabbing onto a branch, pulling and pulling. You can hear voices, like they are far off in the distance. The world goes bright white.

Return to the group. As soon as Hope and Jaroo fall over, Cleric Calmet runs over to them. If you ask him what's going on he simply tell you to trust him. If you check Hope's body you'll feel that she is dead.
Once allowed to do his thing, Calmet will lay his hands on both of them and bow his head in prayer. "Saint Zeller I come to you in a moment of woe. These two faithful servants are are on a just a dutiful quest to rid your world of evil. Channel your power through my hands and allow them to return. This I pray." His hand glow with white radiant energy and that energy encompasses Hope and Jaroo. Calmet releases his hands and both of their eyes pop open and the color returns to their forms. They were only dead for a few seconds. There is a grayish tree branch laying nearby, smoking as if it had been on fire. 
Jaroo will explain that the orange fungus came from the Shadowfell, the realm of darkness and decay. In the realm of shadows it keeps everything in a perpetual state of death and rot. He takes the branch and plants it like a tree in a small circle of stones. It was unlikely an accident that this was brought to the Firbolg Grove.  The perpetrator may not have had the chance without Hope's involvement, but who ever it was seized the opportunity. There is much evil on the move in the all of Toril. The necromancer, this fungus, the rumors coming from Orlane, and the disappearance of Turrim. None of this bodes well for the world.
Jaroo will explain he is too old to accompany the party, but will do what he can. He will study the fungus and asks Hope to return as she continues her journey. Find out how this evil came into our world and only at the source will a cure be found. It will not be easy, but it can be done.