Adult Red Dragon
Huge Dragon, chaotic evil
18,000 XP
Special Abilities
Legendary Resistance (3/Day)
If the dragon fails a saving throw, it can choose to succeed instead.
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 10 ft., one target. Hit: 19 (2d10 + 8) piercing damage plus 7 (2d6) fire damage.
Claw
Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 15 (2d6 + 8) slashing damage.
Tail
Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit: 17 (2d8 + 8) bludgeoning damage.
Frightful Presence
Each creature of the dragon's choice that is within 120 ft. of the dragon and aware of it must succeed on a DC 19 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.
Fire Breath (Recharge 5-6)
The dragon exhales fire in a 60-foot cone. Each creature in that area must make a DC 21 Dexterity saving throw, taking 63 (18d6) fire damage on a failed save, or half as much damage on a successful one.
Legendary Actions
Detect
The dragon makes a Wisdom (Perception) check.
Tail Attack
The dragon makes a tail attack.
Wing Attack (Costs 2 Actions)
The dragon beats its wings. Each creature within 10 ft. of the dragon must succeed on a DC 22 Dexterity saving throw or take 15 (2d6 + 8) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.
Quick Reference
Running This Encounter
An Adult Red Dragon is a legendary creature that should dominate the battlefield through superior positioning and legendary actions. Use its flying speed to maintain distance while dealing massive damage with its multiattack and breath weapon. Leverage lair actions if this is its home, forcing the party to adapt to environmental hazards. Remember that this is a solo monster—consider adding 2-3 lower-CR minions to increase action economy and threaten the party's resources.
Combat Tactics
The dragon opens with its breath weapon (15d6 damage, DC 19 DEX save) against grouped enemies, then uses Multiattack to strike high-threat targets. It prioritizes maintaining flight and distance, using legendary actions to attack or move every round, forcing melee combatants to close gaps while ranged attackers struggle with damage output.
Environment & Setting
An active volcano, mountain peak, or grand throne room within its hoard-filled lair provides the ideal setting. The terrain should offer the dragon high ground, multiple levels for flying maneuvers, and opportunities for lair actions like collapsing structures or lava flows.