Innate Resistance. In addition to its previously established resistances, the dragon has resistance to the damage type corresponding to its color.

Lightning Absorption. If hit with lightning damage, mark how much damage is dealt, that damage is added to a separate pool of 70 temporary hp only accessed by lightning damage. These temporary hitpoints reset each time the dragon uses its Electric Discharge. If all of these hitpoints are exhausted, the lightning overloads the dragon, as it takes 35 lightning damage, this feature and the Electric Discharge feature cannot be used again until a long rest.

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

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 10 ft., one target. Hit: 17 (2d10+6) [piercing] damage + 5 (2d4) [acid] damage

Claw. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 14 (2d6+6) [slashing] damage

Tail Cannon. Ranged Weapon Attack: +13 to hit, range 30/60 ft., one target. Hit: 17 (2d12+4) [bludgeoning] damage. 

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 14 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.

Breath Weapon (Recharge 5-6). The dragon uses its breath weapon to spew a mixture of chemical gas in a 60 ft. cone. Each creature inside must make a DC 18 constitution saving throw or be subject to one of the following effects by rolling a d6. (1-2) Sleep Gas: The creature goes to sleep immediately on a failed save if under 35 hp, on a successful save no effect occurs. (3-4) Poison Gas: On a failed save the creature takes 21 (6d6) [poison] damage, on a successful save they take half as much damage. (5-6) Blinding Gas: On a failed save the creature is blinded for the next 18 seconds, on a successful save no effect occurs. The gas dissipates after this turn.

Disrupting Screech (3/day). The dragon notices a spell being cast, and as a reaction, may cast Counterspell at a 4th level, as its screech disrupts the targets focus momentarily.

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.

Tail Cannon. The dragon uses its tail cannon.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 19 Dexterity saving throw or take 13 (2d6 + 6) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.

Lightning Discharge (Costs 2 Actions). If a creature has dealt lightning damage to the dragon, it can redirect the lightning back, dealing an amount of damage equal to the amount of hit points missing from its temp hp pool.

Enter the description for how mythic actions work for your monster here.

Mythic Action Name (Costs # Actions). Enter the description for your mythic action.