Nightmare

Creature 6

Large
beast
fiend
unholy

Perception: +14; darkvision
Languages: Chthonian, Daemonic, Diabolic
Skills: Acrobatics +13, Athletics +16, Intimidation +14, Survival +12; Str +6, Dex +3, Con +3, Int +1, Wis +4, Cha +2

AC: 24; Fort +15, Ref +15, Will +12
HP: 100; Resistances fire 10

Smoke (aura) 15 feet.

The nightmare continually exhales black smoke. Creatures within the aura are Concealed to those outside it, and creatures outside the aura are concealed to creatures within it. Nightmares and their riders can see through this smoke.

A creature that begins its turn in the area must succeed at a DC 23 Fortitude save or be Sickened 2. It's then temporarily immune to being sickened by the smoke for 1 minute. This is an inhaled poison, and the nightmare and its rider are immune to it.

Speed: 40 feet, fly 90 feet

Melee ◆ jaws +16 (magical, unarmed, unholy), Damage 2d10+8 piercing

Melee ◆ hoof +16 (agile, fire, magical, unholy), Damage 1d8+8 bludgeoning plus 1d6 fire

Divine Innate Spells DC 24, attack +16; 7th interplanar teleport (self and rider only)

Flaming Gallop ◆◆ (divine, fire, unholy) The nightmare Strides or Flies up to triple its Speed. Its hooves burst with intense flame, dealing 3d6 fire damage with a DC 24 basic Reflex save to each creature other than the nightmare's rider that the nightmare moves adjacent to during its gallop. Each creature can be affected only once during a single use of Flaming Gallop.

Source: Pathfinder Monster Core

Running this fight? Add the nightmare to the initiative tracker: type its name and the AC, hit points and Perception for initiative fill in, and the book button shows this stat block mid-fight.