Mushroom Dragon

Traits

Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Magic Resistance. The dragon has Advantage on saving throws against spells and other magical effects.

Magic Weapons. The dragon's weapon attacks are magical.

Mycelial Sight. While the dragon is within 100 feet of the pleurossa network, its Blindsight extends as far as the network reaches and it is immune to the Blinded condition.

Toxic Spores. A creature that starts its turn within 20 feet of the dragon must succeed on a DC 22 Constitution saving throw or gain one level of corruption. Creatures that don't need to breathe are immune to this effect.

Actions

Multiattack. The dragon can use its Overwhelming Spores. It then makes three attacks: one with its bite, one with its corrupting claws, and one with its tail.

Bite. Melee Attack Roll: +15, reach 10 ft. Hit: 34 (4d12 + 8) Piercing damage.

Corrupting Claws. Melee Attack Roll: +15, reach 15 ft. Hit: 26 (4d8 + 8) Slashing damage, and the target must succeed on a DC 22 Constitution saving throw or gain one level of corruption. Floral dragons have Disadvantage on the save.

Tail. Melee Attack Roll: +15, reach 10 ft. Hit: 22 (4d6 + 8) Bludgeoning damage. If the target is a creature, it must succeed on a DC 23 Strength saving throw or be knocked Prone.

Overwhelming Spores. The dragon releases a cloud of spores. Wisdom Saving Throw: DC 16, each creature of the dragon's choice that is within 120 feet of the dragon and aware of it. Failure: Target has the Charmed condition for 1 minute. On its turn, a Charmed creature must move up to its speed toward the dragon by the most direct route possible. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Overwhelming Spores for the next 24 hours.

Corrupting Fungal Presence (Recharge 5+). The dragon exhales putrid spores. Dexterity Saving Throw: DC 22, each creature in a 120-foot Cone. Failure: 32 (5d12) Poison damage and 32 (5d12) Necrotic damage and gains a level of corruption. Success: Half damage only.

Reactions

Spore Sacrifice. When the dragon would take damage, it can use its reaction to halve the damage and force a creature of its choice within 300 feet of the dragon that has 3 or more levels of corruption to take the other half.

Legendary Actions

The dragon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Move. The dragon moves up to half its speed.

Tail Attack. The dragon makes a tail attack.

The Pleurossa's Lair

The pleurossa fully infests the forest where it merged with Izora. There is no place its mycelial tendrils do not reach. While the mushroom dragon is within its area, the pleurossa can take lair actions.
Lair Actions. On initiative count 20 (losing initiative ties), the pleurossa takes a lair action to cause one of the following effects; the pleurossa can't use the same effect two rounds in a row.

• The pleurossa summons a corrupted floral dragon of CR 4 or lower to aid the mushroom dragon in combat. Roll initiative for the corrupted floral dragon. The pleurossa can use this lair action twice per day.
• Glittering spores fill the air in a 20-foot Cube. Each creature within that area must succeed on a DC 15 Dexterity saving throw or be affected as if by the Faerie Fire spell.
• The pleurossa network unearths itself in a 20-foot radius centered on a point on the ground within 120 feet of the mushroom dragon. The area becomes Difficult Terrain and each creature in that area must succeed on a DC 19 Strength saving throw or be Restrained by roots until the pleurossa takes another lair action. A creature can be freed if it or another creature takes an action to make a DC 15 Strength check and succeeds.

Regional Effects. The region containing the pleurossa is warped by its presence, which creates one or more of the following effects:

• Water sources within 5 miles of the lair are contaminated. A creature that drinks the water is Poisoned for 1d4 + 1 hours after ingesting it.
• Plants and animals appear sickly, and the forest is eerily silent as no birds sing here.
• The mushrooms that grow in the forest are corrupted. A creature that ingests a mushroom must succeed on a DC 22 Constitution saving throw or gain one level of corruption.

If the pleurossa dies, these effects fade over the course of 1d10 days.