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: +14 to hit, reach 15 ft., one target. Hit: (2d10 + 6) piercing damage.   Claw. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: (2d8 + 6) slashing damage. If the target is a Huge or smaller creature, it is grappled (escape DC 16 (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: +14 to hit, reach 20 ft., one target. Hit: (2d10 + 6) 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 21 (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.   Perfect Stance. The dragon activates a start of hyper awareness, while in this state attacks against the dragon have disadvantage and the dragon has advantage on all saving throws, gains the evasion feature (When you are subjected to an effect that allows you to make a Dexterity saving throw to take only half damage, you instead take no damage if you succeed on the saving throw, and only half damage if you fail.) and advantage on dexterity and wisdom ability checks. This lasts for 1 minute or until the dragon takes any damage.   Fire Breath (Recharge 5-6). The dragon exhales fire in an 300-foot line that is 10 feet wide. Each creature in that line must make a DC 17 (8 + Prof + Dex) Dexterity saving throw, taking 117 (26d8) fire 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.   Mystic Eye. The dragon creates an invisible sensor somewhere within 300ft of it, the dragon can see through this sensor as if the dragon was occupying it's space. This sensor lasts until the end of the dragons next turn.   Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 30 ft. of the dragon must succeed on a DC 21 (8 + Prof + Str) Dexterity saving throw or take 12 (2d6 + 5) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.  

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 21 (8 + Prof + Cha) Constitution saving throw or take 19 (3d12) thunder damage and be incapacitated until the end of its next turn.   Perfect Stance (Costs 3 Actions). The greatwyrm uses its Perfect Stance action.

Lair Actions

On initiative count 20 (losing initiative ties), the dragon takes a lair action to cause one of the following effects:  

• A strong wind blows around the dragon. Each creature within 60 feet of the dragon must succeed on a DC 15 Strength saving throw or be pushed 15 feet away from the dragon and knocked prone. Gases and vapors are dispersed by the wind, and unprotected flames are extinguished. Protected flames, such as lanterns, have a 50 percent chance of being extinguished.
• A cloud of sand swirls about in a 20-foot-radius sphere centered on a point the dragon can see within 120 feet of it. The cloud spreads around corners. Each creature in it must succeed on a DC 15 Constitution saving throw or be blinded 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.

A brass dragon’s desert lair is typically a ruin, canyon, or cave network with ceiling holes to allow for sunlight.

Regional Effects

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

• Tracks appear in the sand within 6 miles of the dragon’s lair. The tracks lead to safe shelters and hidden water sources, while also leading away from areas that the dragon prefers to remain undisturbed.
• Images of Large or smaller monsters haunt the desert sands within 1 mile of the dragon’s lair. These illusions move and appear real, although they can do no harm. A creature that examines an image from a distance can tell it’s an illusion with a successful DC 20 Intelligence (Investigation) check. Any physical interaction with an image reveals it to be an illusion, because objects pass through it.
• Whenever a creature with an Intelligence of 3 or higher comes within 30 feet of a water source within 1 mile of the dragon’s lair, the dragon becomes aware of the creature’s presence and location.

  If the dragon dies, the tracks fade in 1d10 days, but the other effects fade immediately.