Action Surge. On his turn, he can take one additional action. He can use it twice before a short or long rest, but only once on the same turn.

As an action, he can unleash a 30-foot cone of destructive energy from his weapon. Each creature in that area must make a DC 16 Dexterity saving throw, taking 8d6 lightning damage on a failed save, or half as much damage on a successful one. Once this action is used, it can't be used again until the next dawn.

Indomitable. He can reroll a saving throw that you fail. He can use this feature three times between long rests.

Multi-Attack. Adam Smasher gets 3 attacks.

Unarmed Strike. Melee Weapon Attack: +8 to hit, reach 5 ft., 1 target. Hit: 8 (1d6 + 4) bludgeoning damage.

Wakened Bronze Dragon's Wrath Automatic Rifle. Ranged Weapon Attack: +10 to hit, range 80/240 ft., 1 target. Hit: 15 (2d8 + 6) piercing damage, 7 (2d6) lightning damage.

Burst Fire. A weapon that has the burst fire property can make a single-target attack, or it can spray a 10-foot-cube area within normal range with shots. Each creature in the area must succeed on a DC 15 Dexterity saving throw or take the weapon's normal damage. This action uses ten pieces of ammunition.

Second Wind. He can use a bonus action to regain hit points equal to 1d10 + 11. Once he uses this feature, he must finish a short or long rest before he can use it again.

Adam Smasher can take 3 legendary actions.

Frag Grenade (Costs 1 Action). He can throw a grenade at a point up to 60 feet away. Each creature with 20 feet of an exploding fragmentation grenade must make a DC 15 Dexterity saving throw, taking 5d6 piercing damage on a failed save, or half as much damage on a successful one.

Smoke Grenade (Costs 1 Actions). He can throw a grenade at a point up to 60 feet away. One round after a smoke grenade lands, it emits a cloud of smoke that creates a heavily obscured area in a 20-foot radius. A moderate wind (at least 10 miles per hour) disperses the smoke in 4 rounds; a strong wind (20 or more miles per hour) disperses it in 1 round.

A.M.P. Grenade (Costs 2 Actions). He can throw a grenade at a point up to 60 feet away. The grenade produces an Antimagic Field in a 20 foot radius for 1 round after it is activated. Additionally, each creature within the radius must make a DC 15 Dexterity saving throw, taking 3d6 lightning damage on a failed save, or half as much damage on a successful one.

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

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