Legendary Resistance (3/Day).
If the dragon fails a saving throw, it can choose to succeed instead.
Magma Aura.
A creature that starts their turn within 15 feet of the blackfire dragon takes 6 (3d4) Fire damage. Additionally, any nonmagical weapon or armor equipped or on the creature's person takes a permanent -1 penalty to its AC bonus (for armor) or its attack rolls (for weapons). This penalty stacks and is cumulative. If the penalty ever reaches a -4 total, the armor or weapon is melted and destroyed. Affected (unmelted) armor or and weapons can be repaired via crafting with appropriate toolsets or with proper magic.
Multiattack.
The blackfire dragon makes three attacks: one with its bite and two with its claws. The dragon can replace one of these attacks with a swallow attack.
Bite.
Melee Weapon Attack: +13 to hit, reach 10 ft., one target.
Hit: 17 (2d10+7) Piercing + 7 (2d6) Fire (or Necrotic) damage.
Claw.
Melee Weapon Attack: +13 to hit, reach 5 ft., one target.
Hit: 13 (2d6+7) Slashing damage.
Gore.
Melee Weapon Attack: +13 to hit, reach 10 ft., one target.
Hit: 15 (2d8+7) Piercing damage and the struck target is grappled on the dragon's horn (escape DC 15).
Swallow.
The dragon makes one bite attack against a Large or smaller target it is grappling with its horns. If the attack hits, the target is also swallowed, and the grapple ends. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the dragon, and it takes 21 (6d6) Fire (or Necrotic) damage at the start of each of the dragon's turns.
If the dragon takes 30 damage or more in a single turn from a creature inside it, the dragon must succeed on a DC 21 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the dragon. If the dragon dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 20 feet of movement, exiting prone.
Blackfire Breath (Recharge 5-6).
The blackfire dragon exhales black fire in a 60 foot cone. Each creature in the cone's area must make a DC 21 Dexterity saving throw, taking 63 (18d6) Fire (or Necrotic) damage on a failed save or half as much on a successful save.
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.
Move.
The blackfire dragon moves up to its speed.
Ravage.
The blackfire dragon makes a gore attack with its horns or a claw attack.
Magma Summoning (Recharge 5-6) (Costs 2 Actions).
The blackfire dragon summons 2d4+1 Magma Mephits.
Lair and Lair Actions
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:
- The blackfire dragon causes magma geysers to rise from the floor. Three points (5 foot squares) within the lair erupt with 15 foot high magma geysers at the end of the round. A creature on the chosen point at the start of the round takes 3 (1d6) for standing on the heated area. A creature standing within a 5 foot radius of a geyser when it erupts at the end of the round must make a DC 15 Dexterity saving throw or take 6 (2d6) Fire damage, taking only half as much on a success. The chosen points then become difficult terrain and can't be used as geyser points again for 1 hour. The dragon is not affected by the difficult terrain from the magma geyser.
- A point in the dragon's lair becomes extremely overwhelmed with intense heat. All flammable objects within a 10 foot radius of the chosen point in the lair immediately catch on fire.
- The blackfire dragon causes a portion of the ground to become covered in magma. The dragon chooses a single point within their lair. Once chosen, magma immediately forms and covers a 10 foot radius surrounding the chosen point. The area is considered difficult terrain and any creature that moves into the area immediately takes 9 (3d6) fire damage. This magma lasts until the end of the next round.
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