Actions

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.   Bite. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: (2d10 + 4) piercing damage plus (4d8)poison damage..   Claw. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: (2d8 + 4) slashing damage. If the target is a Huge or smaller creature, it is grappled (escape DC 14 (10+Athletics)) and is restrained until this grapple ends. The greatwyrm can only have one creature grappled this way at a time.   Tail. Melee Weapon Attack: +12 to hit, reach 20 ft., one target. Hit: (2d10 + 4) bludgeoning damage. If the target is a creature, it must make a DC 22 (8 +Prof + Str) Strength saving throw or be knocked prone   Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 28 (8 + Prof + Cha) Wisdom saving throw or become frightened for 1 minute. 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 Frightful Presence for the next 24 hours.   Invoke Duplicate. The dragon creates an illusionary duplicate of itself at a point it can see within 500ft of it. The duplicate is a perfect recreation of the dragon at the time of creation including any object it is wearing or carrying, along with any sounds, smells, and temperature it would create, but it is intangible. A creature that uses its action to examine the duplicate can determine that it is an Illusion with a successful DC 24 (8 +Prof + Int) Intelligence (Investigation) check. The dragon can move the duplicate up to 80ft as a bonus action. This duplicate last for 1 hour or the dragon uses this ability again.   Poison Breath (Recharge 5-6). The dragon exhales poisonous gas in a 300-foot cone. Each creature in that area must make a DC 23 (8 + Prof + Con) Constitution saving throw, taking 99 (22d8) poison damage on a failed save, or half as much damage on a successful one.   Change Shape. The dragon magically polymorphs into a Humanoid or beast that has a Challenge rating no higher than its own, or back into its true form. It reverts to its true form if it dies. Any Equipment it is wearing or carrying is absorbed or borne by the new form (the dragon's choice). In a new form, the Dragon retains its Alignment, Hit Points, Hit Dice, ability to speak, Proficiencies, Legendary Resistance, lair Actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its Statistics and capabilities are otherwise replaced by those of the new form, except any Class Features or legendary Actions of that form.

Legendary Actions

The greatwyrm 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 greatwyrm regains spent legendary actions at the start of their turn.   Detect. The dragon makes a Wisdom (Perception) check.   Attack. The dragon makes a claw or tail attack.   Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 30 ft. of the dragon must succeed on a DC 26 (8 + Prof + Str) Dexterity saving throw or take 11 (2d6 + 4) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.   Shift. The dragon and it's duplicate teleport to each other's spaces, any object the dragon is wearing or carrying is teleported along with it. The dragon cannot take this action if another creature is occupying the duplicates space.  

Mythic Actions

If the greatwyrm's Draconic Awakening trait has activated in the last hour, it can use the options below as legendary actions.   Bite. The greatwyrm makes a bite attack.   Shattering Roar (Costs 2 Actions). The greatwyrm unleashes a magical roar. Each creature in a 120-foot-radius sphere centered on the greatwyrm must succeed on a DC 28 (8 + Prof + Cha) Constitution saving throw or take 19 (3d12) thunder damage and be incapacitated until the end of its next turn.   Invoke Duplicate (Costs 3 Actions). The greatwyrm uses its Invoke Duplicate action.

Lair Actions

On initiative count 20 (losing initiative ties), the dragon takes a lair action to cause one of the following effects; the dragon can’t use the same effect two rounds in a row:  

• Grasping roots and vines erupt in a 20-foot radius centered on a point on the ground that the dragon can see within 120 feet of it. That area becomes difficult terrain, and each creature there must succeed on a DC 15 Strength saving throw or be restrained by the roots and vines. A creature can be freed if it or another creature takes an action to make a DC 15 Strength check and succeeds. The roots and vines wilt away when the dragon uses this lair action again or when the dragon dies.
• A wall of tangled brush bristling with thorns springs into existence on a solid surface within 120 feet of the dragon. The wall is up to 60 feet long, 10 feet high, and 5 feet thick, and it blocks line of sight. When the wall appears, each creature in its area must make a DC 15 Dexterity saving throw. A creature that fails the save takes 18 (4d8) piercing damage and is pushed 5 feet out of the wall’s space, appearing on whichever side of the wall it wants. A creature can move through the wall, albeit slowly and painfully. For every 1 foot a creature travels through the wall, it must spend 4 feet of movement. Furthermore, a creature in the wall’s space must make a DC 15 Dexterity saving throw once each round it’s in contact with the wall, taking 18 (4d8) piercing damage on a failed save, or half as much damage on a successful one. Each 10-foot section of wall has AC 5, 15 hit points, vulnerability to fire damage, resistance to bludgeoning and piercing damage, and immunity to psychic damage. The wall sinks back into the ground when the dragon uses this lair action again or when the dragon dies.
• Magical fog billows around one creature the dragon can see within 120 feet of it. The creature must succeed on a DC 15 Wisdom saving throw or be charmed by the dragon until initiative count 20 on the next round.

The forest-loving green dragons sometimes compete for territory with black dragons in marshy woods and with white dragons in subarctic taiga. However, a forest controlled by a green dragon is easy to spot. A perpetual fog hangs in the air in a legendary green dragon’s wood, carrying an acrid whiff of the creature’s poison breath. The moss-covered trees grow close together except where winding pathways trace their way like a maze into the heart of the forest. The light that reaches the forest floor carries an emerald green cast, and every sound seems muffled.   At the center of its forest, a green dragon chooses a cave in a sheer cliff or hillside for its lair, preferring an entrance hidden from prying eyes. Some seek out cave mouths concealed behind waterfalls, or partly submerged caverns that can be accessed through lakes or streams. Others conceal the entrances to their lairs with vegetation.

Regional Effects

The region containing a legendary green dragon’s lair is warped by the dragon’s magic, which creates one or more of the following effects:  

• Thickets form labyrinthine passages within 1 mile of the dragon’s lair. The thickets act as 10-foot-high, 10-foot-thick walls that block line of sight. Creatures can move through the thickets, with every 1 foot a creature moves costing it 4 feet of movement. A creature in the thickets must make a DC 15 Dexterity saving throw once each round it’s in contact with the thickets or take 3 (1d6) piercing damage from thorns. Each 10-foot-cube of thickets has AC 5, 30 hit points, resistance to bludgeoning and piercing damage, vulnerability to fire damage, and immunity to psychic and thunder damage.
• Within 1 mile of its lair, the dragon leaves no physical evidence of its passage unless it wishes to. Tracking it there is impossible except by magical means. In addition, it ignores movement impediments and damage from plants in this area that are neither magical nor creatures, including the thickets described above. The plants remove themselves from the dragon’s path.
• Rodents and birds within 1 mile of the dragon’s lair serve as the dragon’s eyes and ears. Deer and other large game are strangely absent, hinting at the presence of an unnaturally hungry predator.

  If the dragon dies, the rodents and birds lose their supernatural link to it. The thickets remain, but within 1d10 days, they become mundane plants and normal difficult terrain, losing their thorns.