Azhdaha

Immutable Form. Azhdaha is immune to any spell or effect that would alter its form.

Siege Monster. Azhdaha deals double damage to objects and structures.

Lumbering Form.  Because Azhdaha is so large, it costs 5 ft of movement to turn 90 degrees.

Legendary Resistance (4/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Residual Damage. When a creature is dealt Fire, Lightning, Cold, or Acid damage if their AC is less than 15 they take an additional 1d8 of the dealt damage at the start of the next 4 turns. Taking Fire, Lightning, Cold, or Acid damage again will reset the duration. 

Limited Magical Weapons. Azhdaha's attacks that deal Fire, Lightning, Cold, and Acid damage are considered magical.

Unabsolved (Mythic Trait, Recharges after a Short or Long Rest). When Azhdaha would have his hit points reduced by a third, Azhdaha gains immunity to all damage and may no longer take legendary actions until the start of his next turn. At the start of his next turn roll a die, on an even number he enters his Fire Form, and on an odd number, he enters his Acid Form.

Last Stand (Mythic Trait, Recharges after a Short or Long Rest). When Azhdaha would have his hit points reduced by 2/3, Azhdaha gains immunity to all damage and may no longer take legendary actions until the start of his next turn. At the start of his next turn roll a die, on an even number he enters his Cold Form, and on an odd number, he enters his Lightning Form. Additionally, at the start of his next turn, He will burrow into the ground leaving his tail exposed and causing his Tail Effect (listed in Lair Actions) to activate for one turn cycle.  

Burrow. Azhdaha melds into the earth, gaining the ability to use its burrow speed. At the start of his next turn or if he uses a legendary action other than Ground Hunter, he emerges from the ground. He can't use this action two turns in a row.

Stomp. Melee Weapon Attack: +17 to hit, reach 5 ft., 15 ft radius. Hit: 18 (2d12 + 10) (2d12 + 10) bludgeoning damage. Azhdaha raises his foot and stomps down, causing the ground to tremble around his foot. Each other creature within 15 ft of his foot also takes the damage.

Tail Slash. Melee Weapon Attack: +14 to hit, reach 15 ft., radius. Hit: 19 (2d8 + 10) bludgeoning damage. Azhdaha quickly turns in a circle, slaming creatures within 15 ft with his tail.

Tail Smash. Melee Weapon Attack: +15 to hit, reach 20 ft by 10 ft., behind him. Hit: 20 (2d8 + 10) bludgeoning damage. Azhdaha fully extends his tail behind him and slams it down, dealing damage to creatures in a 20 ft by 10 ft area behind him.

Charge. Melee Weapon Attack: +14 to hit, reach up to 20 ft., area. Hit: 20 (2d8 + 10) bludgeoning damage. Azhdaha Spends the rest of his movement for the turn to charge farward in a strait line 15 ft wide, dealing damage to creatures within the line.

Body Slam. Melee Weapon Attack: +17 to hit, reach 20 ft, radius. Hit: 10 (1d8 + 10) bludgeoning damage. Azhdaha Leaps into the air and crashes down, dealing damage to any creature within 20 ft and forcing them to make a DC 18 Strength saving throw. On a failure they are kocked back 15 ft from Azhdaha. This can only be used if Azhdaha hasn't moved this turn, additionaly useing this attack reduces his speed to 0 until the start of the next turn.

Wrath of The Rock. RangedWeapon Attack: +12 to hit, reach 40 ft, 4 targets. Hit: 18 (2d8 + 10) bludgeoning damage. Azhdaha launches out 4 rock lances from his back that seek out creautres in range.

Azhdaha can take 4 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. Azhdaha regains spent legendary actions at the start of its turn.

Ground Hunter (Costs 2 Actions, must be underground). Azhdaha partially emerges from the ground and moves up to his burrow speed in a straight line. Creatures in the line must make a DC 17 Dexterity saving throw or take 15 (2d12) bludgeoning damage and be knocked prone on a failure, half damage, and not knocked prone on a success.

Rampage (Costs 1 Action). Azhdaha proforms a Stomp, Tail Slash, Tail Smash, Charge, or Body Slam attack. 

When Azhdaha's Unabsolved or Last Stand mythic trait is active, He can use the options below as Legendary actions for 1 hour. Unless it specifies a form, the attacks will deal Acid damage if he is in Acid Form or Fire damage if he is in Fire form.

Elemental Rampage (Costs 1 Action). Azhdaha performs a Body Slam or Stomp attack.

When Azhdaha's Last Stand mythic trait is active, He can use the options below as Legendary actions for 1 hour. Unless it specifies a form, the attacks will deal Cold damage if he is in Cold Form or Lightning damage if he is in Lightning form.

Frostborn Perl (Cold Form, Costs 2 Actions, 1/day). Azhdaha summons a floating orb of ice. At the start of the next 5 turns, it will shoot an icicle lance at each creature of Azhdaha's choice. Creatures targeted must make a DC 15 Dexterity saving throw or take 1d12 cold damage on a failure. On a success, the creature may move 5 ft in any direction. 

Shooting Stars (Lightning Form, Costs 2 actions, 1/day). Azhdaha summons 6 spheres of electricity above his tail. He then sends them at 6 creatures, he may target the same creature with multiple spheres. Creatures targeted by a sphere must make a DC 15 Dexterity Saving throw or take 3d12 Lightning damage on a failure for each sphere. On a success, the creature my move 5 ft in any direction.

Booming Swing (Costs 1 Action). Azhdaha performs a Tail Slash attack. His tail will leave behind 3 bombs in different places along the edge of the attack. Afterward, they will explode dealing 12 (2d8) damage.

Enraged Earth (Costs 1 Action). Azhdaha performs a Charge, Wrath of the Rock, or Tail Smash attack