Ancient Forest Dragon

Legendary Resistance (6/Day). If the dragon fails a saving throw, it can choose to succeed instead. The dragon cannot be killed by the wish spell.

Immortal. The dragon cannot be damaged unless at the start of combat, a wish spell is cast to take away its imortality. The dragon can voluntarily take away its own immortality. The dragon regains its immortality at the end of combat.

Acidic Blood. Any weapon or creature that damages the dragon take 6d6 acid damage. Nonmagical weapons and gear are destroyed by the corrosive acid. This acid ignores resistance and immunity. 

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

Consume magic (6/Day). If the dragon is targeted by a spell that deals damage the dragon heals the amount of damage delt instead and all other spell effects are negated.

Sprint. The dragon doubles all its movement for one turn. The dragon can do this at any time. If the dragon has moved on its turn already, it doubles the remaining movement. This does not cost an action.

Earthmover. The dragon can burrow through solid stone, wood and metal as if it were regular terrain. The dragons tunnels it makes while burrowing stay stable unless the dragon chooses to collapse the tunnel behind it. The sinners are big enough for other gargantuan creatures.

Thorny plating. The dragon can spend on action to cover itself in thorny plated scales. This gives the dragon a +10 bonus to Ac and any item or creature that hits it takes 55 (5d10+5) piercing or slashing damage(DM’s choice). These thorns are magical and can not be destroyed. The dragon can spend one action to absorb the thorns into its scales, taking away the bonus to Ac and damage features. If the dragon is targeted with a line spell while with the thorns out, roll a d8, on 1, nothing happens, 2-6, the spell randomly rebounds and hits something else, 7-8, the spell is reflected at the caster.

Forests wrath. The dragon can use an action to roar and magically summon/create a treant that follows its commands and shares the dragons intentions. The treant can speak and understand draconic, but not read it.

Forest Camouflage. While in a forest or a swamp, the dragon can spend an action to magically become invisible for any amount of time, or shrink its size or grow in size. The changes in size do not affect any of the dragons ability or stats other than weight and size.

Siege Monster. The dragon deals double damage to objects and structures.

Innate spellcasting. The dragon has the following spells prepared (save DC 27) and can use them as many times as it pleases and does not need components. The dragons spell casting ability is wisdom. The dragon is a 20th level spell caster.

Cantrips: Thorn whip, True strike, Poison spray, Acid splash, Eldritch blast, Cone of cold, Fire bolt, Chill touch, Frostbite,

1st level: Detect magic, Faire fire, Thunderwave, Inflict wounds, Hail of thorns, Magic missile, Shield, Fog cloud, Hellish rebuke, Ray of sickness, Witch bolt.

2nd level: Protection from poison, Barkskin, Beast sense, Gust of wind, Moonbeam, Magic weapon, Spiritual weapon, Spider climb, Invisibility, Hold person.

3rd level: Elemental weapon, Plant growth, Speak with plants, Water walk, Counterspell, Fireball, Stinking cloud, Lightning bolt, Dispel magic, Wind wall.

4th level: Greater invisibility, Polymorph, Grasping vine, Stoneskin, Giant insect, Wall of fire.

5th level: Greater restoration, Hold monster, Insect plague, Commune with nature,  Tree stride, Conjure volley, Cloudkill, Wall of stone, Wall of force, Destructive wave.

6th level: Chain lightning, Disintegrate, Wall of ice, Sunbeam, Flesh to stone, Eyebite, Blade barrier, Heal, Hero’s feast, Wall of thorns, Move earth, Transport via plants.

7th level: Forcecage, Regenerate, Resurrection, Teleport, Firestorm, Reverse gravity, Prismatic spray, Reverse gravity

8th level: Control weather, Sunburst, Telepathy, Antimagic field, Earthquake, Tsunami, Incendiary cloud, Power word stun.

9th level: Wish, Meteor swarm, Time stop, True polymorph, Shapchange, Weird, Prismatic wall, Power word kill, Astral protection, Gate, Foresight, Imprisionment.

Powerful Magic. The dragons attacks count as magical and treat immunity’s as resistances and ignore resistances. The dragon is immune to spells that would harm it that are below 5th level.

Amphibious. The dragon can breath air and water.

Flyby. The dragon doesn’t provoke an opportunity attack when it flys out of an enemy’s reach. 

Multiattack. The dragon can use its Frightful Presence. It can then make five attacks of its choice.

Bite. Melee Weapon Attack: +15 to hit, reach 40 ft., one target. Hit: 30 (4d10+10) piercing damage.

Swallow. The dragon makes one bite attack against a huge or smaller creature. If the attack hits the target takes the bite damage and is swallowed. While swallowed a creature is prone, restrained, poisoned, blinded, and deafened. A swallowed creature takes 5d6 acid damage, 2d6 slashing damage, and 2d6 bludgeoning damage each round. If a swallowed creature dies, the dragon can swallow another target.

Claw. Melee Weapon Attack: +15 to hit, reach 20 ft., one target. Hit: 35 (5d10+ 10) slashing damage.

Grab. The dragon makes a claw attack against a large or smaller creature. A small or smaller creature will be killed if hit. If the attack hits the target takes no damage(unless it’s small or tiny) and is instead grabbed by the dragon and grappled and restrained unless the dragon chooses not to restrain the creature (Dc 30 strength save).The dragon can the set the creature down, continue to hold the creature, or throw the creature up to 100 ft. A thrown creature makes a Dc 30 dexterity save. On a failed save 68 (10d6+8) bludgeoning damage. Of success, half damage.

Tail. Melee Weapon Attack: +15 to hit, reach 90 ft., all targets in range. Hit: 74 (8d8+10) bludgeoning or piercing damage (dm’s choice) and the targets are knocked prone.

Thorn shot. Ranged Weapon Attack: + 15 to hit, reach 150/300 ft., one target. Hit: 22 (3d6+4) piercing damage and 14 (2d6+2) poison damage. The dragon can attack up to six times with this attack for one attack action.

Vine whip. Melee Weapon Attack. +15 to hit, reach 50 ft., one target. Hit: 38 (3d10+8) slashing damage and 38 (3d10+8) bludgeoning damage.

Spear throw. The dragon magically creates a giant spear of wood and hurls it at an enemy. This attack can be affected by the conjure volley spell. 
Ranged Weapon Attack: +15 to hit, reach 150/600ft., one target. Hit: 69 (5d10+19) piercing damage.

Tree Spike. A 600 ft tall tree sprouts at any point the dragon can see. If the dragon looks at a creature, the creature takes 25d20 piercing damage and is impaled on the tree. If the creature frees itself, it falls and takes 15d10 bludgeoning damage. The tree is difficult terrain for all creatures except the dragon even if they can climb. This damage ignores resistance and immunity. If the target is a large or smaller creature, the target dies.

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 19 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 12 hours.

Breath Weapons (Recharge 5–6)  

The dragon uses one of the following breath weapons.

Acid Breath. The dragon exhales acid in an 160-foot line that is 10 feet wide. Each creature in that line must make a DC 29 Dexterity saving throw, taking 111 (16d12+15) acid damage on a failed save, or half as much damage on a successful one.

Lightning Breath. The dragon exhales green lightning in a 600-foot line that is 10 feet wide. Each creature in that line must make a DC 29 Dexterity saving throw, taking 210 (21d10) lightning damage on a failed save, or half as much damage on a successful one. This lightning can chain to any amount of creatures within a 600 ft radius of the dragon. Each creature takes full damage. On 20 to hit, any creature hit becomes paralyzed for 2 minutes.

Poison Breath. The dragon exhales toxic gas in a 90-foot cone. Each creature in that area must make a DC 30 Constitution saving throw, taking 225 (20d10+25) poison damage on a failed save and half as much on a successful one. Any creature hit by this breath weapon becomes poisoned and one other random condition. Roll a d10. 1-blinded, 2-charmed, 3-deafened, 4-exhausted, 5-frightened, 6-incapacitated, 7-paralyzed, 8-petrified, 9-stunned, 10-uncosious. 

Slowing Breath. The dragon exhales gas in a 120-foot cone. Each creature in that area must succeed on a DC 28 Constitution saving throw. On a failed save, the creature can't use reactions, its speed is halved, and it can't make more than one attack on its turn. In addition, the creature can use either an action or a bonus action on its turn, but not both. These effects last for 1 minute. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself with a successful save. 

Paralyzing Breath. The dragon exhales paralyzing gas in a 120-foot cone. Each creature in that area must succeed on a DC 29 Constitution saving throw or be paralyzed 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.

Weakening Breath. The dragon exhales gas in a 120-foot cone. Each creature in that area must succeed on a DC 30 Strength saving throw or have disadvantage on Strength-based attack rolls, Strength checks, and Strength saving throws 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.

Repulsion Breath. The dragon exhales repulsion energy in a 120-foot cone. Each creature in that area must succeed on a DC 29 Strength saving throw. On a failed save, the creature is pushed 180 feet away from the dragon and knocked prone.

Sleep Breath. The dragon exhales sleep gas in a 120-foot cone. Each creature in that area must succeed on a DC 27 Constitution saving throw or fall unconscious  for 10 minutes. This effect ends for a creature if the creature takes damage or someone uses an action to wake it.

Vampiric Breath. The dragon targets a creature within 600 ft of itself. That creature takes 420 (10d20+20) necrotic damage. If this damage reduces a creature to 0 Hp, the creature makes no death saving throw and crumbles to ashes. The dragon heals the amount of health equal to the amount of damage dealt. This damage ignores resistance and immunity. This breath weapon does not need to recharge.

Change Shape. The dragon magically polymorphs into a creature that has a challenge rating equal to at lower 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.

Innate spellcasting. The dragon can cast one spell of any level as a bonus action. 

Counter. When the dragon is hit it can use its reaction to make an attack or cast a spell.

Block. The dragon makes a constitution saving throw. DC= what the attacker rolled to hit. On success, half damage.

The dragon can take 5 legendary actions, choosing from the options below. 5 legendary actions can be use at a time. Legendary actions can be used the end of another creature's turn. The dragon regains spent legendary actions at the start of its turn.

Roar. The dragon roars deafeningly. This roar is audible in a 600 ft radius around the dragon all creatures in the radius become frightened, deafened, and stunned.

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

Tail Attack. The dragon makes a tail attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 60 feet of the dragon must succeed on a DC 26 Dexterity saving throw or take 26 (6d6 + 8) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.