Ancient Brass Dragon

From Monster Manual, page 104.

**Hit Points:** 297 (17d20 + 119)
 **STR**
27 (+8)
10 (0)
25 (+7)
16 (+3)
15 (+2)
 **Saving Throws:** Dex +6, Con +13, Wis +8, Cha +10
**Skills:** History +9, Perception +14, Persuasion +10, Stealth +6
**Damage Immunities:** fire
**Senses:** blindsight 60 ft., darkvision 120 ft., passive Perception 24
**Languages:** Common, Draconic
 ***Legendary Resistance (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:* +14 to hit, reach 15 ft., one target. *Hit:* 19 (2d10 + 8) piercing damage.
***Claw.** Melee Weapon Attack:* +14 to hit, reach 10 ft., one target. *Hit:* 15 (2d6 + 8) slashing damage.
***Tail.** Melee Weapon Attack:* +14 to hit, reach 20 ft., one target. *Hit:* 17 (2d8 + 8) 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 18 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 Weapons (Recharge 5-6).*** The dragon uses one of the following breath weapons:
* **Fire Breath.** The dragon exhales fire in a 90-foot line that is 10 feet wide. Each creature in that line must make a DC 21 Dexterity saving throw, taking 56 (16d6) fire damage on a failed save, or half as much damage on a successful one.
* **Sleep Breath.** The dragon exhales sleep gas in a 90-foot cone. Each creature in that area must succeed on a DC 21 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.

***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).
 The dragon can take 3 legendary actions, choosing from the options below. Only one legendary action 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.
**Detect.** The dragon makes a Wisdom (Perception) check.
**Tail Attack.** The dragon makes a tail attack.
 On initiative count 20 (losing initiative ties), the dragon takes a lair action to cause one of the following effects; the dragon can't use the same effect two rounds in a row:
* 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.
 The region surrounding 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.