The Demon in the Forest

Overview
The druid Lia, friend of Tavi Gray, has set up residence in the Katarin Jungle. Using the power of the Seed of Melora, she has transformed herself into a great tree in order to seal away a great evil.

Combat Encounter
Trekking through the forest the group sees an odd long puddle of dull green goo. Not long after two Armalugs stumble out from under the roots of two nearby tree from opposite directions, and attack, focusing primarily on whomever has the Alchemy Jug.
 * 2x Armalug (Ixor's Manual of Monsters)

Skill Enounter
The part stumbles out of the jungle into a small clearing. A freshwater pond sits serenely in the middle. Looking about the party sees 4 white shapes with brown and orange spots on them, like Koi. 3 of them are in the water, and one is sitting on a branch overhanging the water, resting. Each of these creatures is about the size of a cat from what they can tell. When noticed, the 3 shapes in the water will dart away into the forest, too fast to catch, but the last will uncoil and look at the party, a Koibra. It looks to each party member in turn, everyone getting a physical sensation of curiosity/wonder/intrigue as it looks at them. Eventually its eyes settle specifically on Widdershins. The creature has an interest in becoming Widdershins' familiar, but he'll have to woo it in some way to gain its loyalty and effection.

Combat Encounter
The party stumbles into a section of forest that is much more thickly vined than they have seen before. Looking around a large spiny maw of plant opens, like a huge flower, and the vegetation begins to tremble and move, the attack begins. Midway through the combat, someone notices the torn up and bloody pile of traveling clothes, notably a dark cloak, along with a traveling pack. Inside the pack is the journal entry from Hiron, the rogue who was traveling with Lia to find the corruption in the jungle.
 * Fliezund (Ixor's)
 * 4x Rayer

Lore Encounter
The party finds an odd tree amidst all the other trees. From the ground around its root there are orange veiny tendrils winding their way up the tree. In odd spots along this veins are large orange bubbles. Unbeknownst to them, the bubbles are filled with Radiance, the corruption from the Pod Demons Lia has trapped in the cave using the Kernel of Melora. Touching one of these bubbles will cause it to pop, per the Detonate ability on the Pod Spawn:
 * Detonate: Creatures within 10 feet must make on a DC 17 Dexterity saving throw, taking 27 (6d8) acid damage on a failed save or half as much damage on a successful one.

Skill Encounter
As the jungle begins to descend into night, the bugs begin to come out in force, in particular the stinging, biting ones. Each member of the party must make a DC15 Con saving throw or become diseased beginning the next adventuring day. The disease functions as follows:
 * Sight Rot: One day after infection, the creature’s vision starts to become blurry. The creature takes a −1 penalty to Attack rolls and Ability Checks that rely on sight. At the end of each Long Rest after the symptoms appear, the penalty worsens by 1. When it reaches −5, the victim is Blinded until its sight is restored by magic such as  Lesser Restoration  or  heal.

Combat Encounter
Bedding down for the evening, the party attracts the attention of some of the jungle's nocturnal predators: caustic ants.
 * 1x Caustic Queen Ant
 * 3x Caustic Soldier Ant
 * 5x Caustic Worker Ant

Adventuring Day 2
The party is finally led to the glade where Lia was last seen. They find a huge tree covering an entrance to a cave heading deep underground. Little does the party know, but the tree is actually Lia, transformed by the power of the Kernel of Melora, guarding a terrible secret deep below.

Combat Encounter
The tree begins to attack, defending the cave entrance. When attacked, the tree will begin to bleed human blood, a clue that something is very amiss here. The attack can be stopped if Tavi calls out Lia's name. The entrance to the cave is covered with thick barbed vines, which will move out of the way once the Tree Guardian being controlled by Lia is pacified.
 * Treant Hurler (attacks have range due to vines erupting from the ground)
 * Ceryntis (MonsterModule p34)
 * 2x Grove Guardians (Monster A Day p40)

Lore Encounter
Near the entrance of the cave the party finds a dessicated corpse, orange good running down its face from its eyes. The corpse is clad in platemail, with gold sun-like patterns at various points in its design, which can be deduced to be a paladin of Pelor. Around it there are many pages of parchment, each scrawled with the same word: "RADIANCE".

Skill Encounter
Amidst the delve into the cave to find Lia, the party finds a tight tunnel that they must crawl through. The tunnel is about 60 feet long and has vines interweaving throughout it. On the vines, about 100 in count, are nodules of Radiant Ichor, along with the orange amber veins connecting them. Touching a nodule will cause it to explode, each creature within 10 feet must make a Constituion saving throw (DC12), rolling on the Indefinite Madness table on a failed save. The nodules regrow after a minute.

Finale Combat Encounter
Arriving at the end of the cave, the party finds an odd sight: a dark skinned woman with long curly white hair (Lia) is kneeling on the ground, as though in prayer. In her outstretched right hand is a what looks like a large ornate seed of some kind, with pulsing green lines of green energy, like vines, coursing over it. From this item (the Kernel of Melora), a conical explosion of what looks like Amber erupts forward, like a jetflame of amber frozen in time. Inside the amber is a robed figure, lithe and menacing, its many robes tattered and frayed. It is mid-lunge, one of its long lithe arms outstretched toward Lia, four long needle-like spines pointed directly at her, a snarl frozen on the gaping maw of teeth on its face. From Lia arms, legs, and back extend a series of tree roots, curling upward into the ceiling, giving rise to the tree guardian above, and the vines covering the entrance to this cave.

Removing the Kernel of Melora will break the spell, the branches and root crumbling away from Lia, unharmed though unconscious from the exhaustion of concentrating for so long. The amber will also shatter, freeing the Cambium to continue its corruption of the forest.
 * Cambium Sovereign:
 * AC: 19
 * HP: 250
 * Speed: 40ft
 * Str+5, Dex+3, Con+6, Int+3, Wis+3, Cha+4
 * Saving Throws: Dex+8, Con+11, Int+8, Wis+8, Cha+9
 * Perception+8
 * Immunities: Poison
 * Resistances: Exhaustion, Poison
 * Legendary Resistances (3/day)
 * Sense: Dark Vision 60ft
 * Languages: Common, Draconic, Infernal
 * Innate Spellcasting (DC17, +9):
 * Constant: Levitate
 * At Will: Alter Self, Detect Thoughts, Hold Person, Plane Shift, Spare the Dying
 * 3/day: Cure Wounds (4d8+3), Ray of Sickness (4d8), Protection From Poison, Heal
 * 1/day: Finger of Death
 * Actions
 * Multiattack, two needle finger attacks
 * Needle Finger Melee Weapon Attack:  +10 to hit, reach 10 ft., one target.  Hit:  21 (3d10 + 5) piercing damage. In addition, the target must make a DC 19 Constitution saving throw; if it fails, the cambium can either inflict Ability Damage or Imbalance Humors. A target makes this saving throw just once per turn, even if struck by more than one needle fingers attack.
 * Ability Damage (3/Day).  When the target of the cambium’s needle fingers fails its Constitution saving throw, one of its ability scores (cambium’s choice) is reduced by 2d4 until it finishes a long rest. If this reduces a score to 0, the creature is unconscious until it regains at least one point.
 * Imbalance Humors (3/Day each).  When the target of the cambium’s needle fingers fails its Constitution saving throw, apply one of the following effects:
 * Sanguine Flux:  The target cannot be healed—naturally or magically—until after their next long rest.
 * Choleric Flux:  The target becomes confused (as the spell) for 3d6 rounds. The target can repeat the saving throw at the end of each of its turns to shrug off the flux before the duration ends.
 * Melancholic Flux:  The target is Incapacitated for 1d4 rounds and slowed (as the Slow spell) for 3d6 rounds. The target can repeat the saving throw at the end of each of its turns to shrug off the flux before the duration ends.
 * Phlegmatic Flux:  A successful DC 18 Constitution saving throw negates this effect. A failed saving throw means the target gains one level of Exhaustion which lasts for 3d6 rounds.
 * Legendary Actions (3 per round)
 * Cast a spell (Costs 2 Legendary Actions)
 * One Needle Finger Attack
 * Healing Ichor - regain 2d8 HP, only usable if standing in an ichor pool.
 * Teleport - pick a space covered by ichor within 40 feet, teleport to it.
 * Lair Actions (Initiative Count 20)
 * Gas Spores - Create 4 pod demon spawn and place them in ichor wherever desired on the map. The Gas Spores explode at the next Initiative Count 20. In addition, add a ten foot radius ichor pool where the spores burst.
 * Three creatures must make Constitution saving throws of DC16, on a fail they roll on the Indefinite Madness table, creatures standing in ichor make this roll at disadvantage.
 * Ichor
 * The Cambium is known to spread its Radiant Ichor as a means of infecting an area. This ichor is highly acidic. A creature who starts their turn in this ichor takes 2d8 acid damage. Ichor is treated as difficult terrain for all purposes.

Magic Items

 * Robe of the Cambium - requires attunement. Charges: 3. While attuned to this robe, you have immunity from poison and disease, and to resistance to acid damage. In addition, when you hit with a single target melee attack you may make the target of that attack must make a Constitution saving throw, DC 19. If they fail the saving throw you may choose to imbalance their humors, pick one effect from below. The target may repeat the saving throw at the end of each of their rounds to remove the effect. Charges regenerate each day at dawn.
 * Sanguine Flux:  The target cannot be healed naturally or magically.
 * Choleric Flux:  The target becomes confused (as the spell).
 * Melancholic Flux:  The target is Incapacitated for 2d4 rounds and slowed (as the Slow spell).
 * Phlegmatic Flux:  The target gains two levels of Exhaustion.
 * Empowered Holy Symbol of Life - requires attunement. While attuned to this item, any healing spells you cast heal an addition 10 + the spell's level per target.
 * Kernel of Melora - requires attunement. Requires a Wisdom check DC23 to attune to. While attuned to this item, the bearer has the following traits and abilities:
 * You are immune to all poisons and diseases, and immune to all poison damage.
 * You may reroll all damage dice of 1 when rolling for damage with a Druid spell.
 * Once per day, you may Shapechange, as per the spell, into a Treant.