Nightmare (CR 5)

Large Outsider (Evil and Extraplanar)
Alignment: Always neutral evil
Initiative: +6 (+2 Dex, +4 Improved Initiative); Senses: darkvision 60 ft., Listen +12, and Spot +12

AC: 24 (-1 size, +2 Dex, +13 natural), touch 11, flat-footed 22
Hit Dice: 6d8+18 (45 hp)
Fort +8, Ref +7, Will +6
Speed: 40 ft., fly 90 ft. (good)
Space: 10 ft./5 ft.
Base Attack +6; Grapple +14
Attack: Hoof +9 melee
Full Attack: 2 hooves +9 melee and bite +4 melee
Damage: Hoof 1d8+4 and 1d4 fire, bite 1d8+2
Special Attacks/Actions: Flaming hooves, smoke
Abilities: Str 18, Dex 15, Con 16, Int 13, Wis 13, Cha 12
Special Qualities: Astral projection, etherealness
Feats: Alertness; Improved Initiative; Run
Skills: Concentration +12, Diplomacy +3 Intimidate +10, Knowledge (the Planes) +10, Listen +12, Move Silently +11, Search +10, Sense Motive +10, Spot +12, and Survival +10 (+12 on other planes and following tracks)
Advancement: 7-10 HD (Large); 11-18 HD (Huge)
Climate/Terrain: Gray Wastes of Hades
Organization: Solitary
Treasure/Possessions: None

Source: Monster Manual

Flaming Hooves (Su): A blow from a nightmare's hooves sets combustible materials alight.

Smoke (Su); During the excitement of battle, a nightmare often snorts and neighs with rage. This fills a 15-foot cone with hot, sulfurous smoke that chokes and blinds opponents. Anyone in the cone must succeed at a Fortitude save (DC 16) suffer a -2 morale penalty to all attack and damage rolls until 1d6 minutes after they leave the cone. The nightmare gains one-half concealment against creatures 5 feet away and total concealment against creatures 10 feet away. The smoke does not obscure the nightmare's vision at all. The nightmare can suppress the smoke as a free action.

Astral Projection and Etherealness (Su): These function just like the spells of the same names cast by a 20th-level sorcerer.

Carrying Capacity: A light load for a nightmare is up to 300 pounds; a medium load, 301- 600 pounds; and heavy load, 601-900 pounds.

Evil Subtype

A subtype usually applied only to outsiders native to the evil-aligned Outer Planes. Evil outsiders are also called fiends. Most creatures that have this subtype also have evil alignments; however, if their alignments change, they still retain the subtype. Any effect that depends on alignment affects a creature with this subtype as if the creature has an evil alignment, no matter what its alignment actually is. The creature also suffers effects according to its actual alignment. A creature with the evil subtype overcomes damage reduction as if its natural weapons and any weapons it wields were evil-aligned (see Damage Reduction).

Extraplanar Subtype

A subtype applied to any creature when it is on a plane other than its native plane. A creature that travels the planes can gain or lose this subtype as it goes from plane to plane. This book assumes that encounters with creatures take place on the Material Plane, and every creature whose native plane is not the Material Plane has the extraplanar subtype (but would not have when on its home plane). An extraplanar creatures usually has a home plane mentioned in its description. These home planes are taken from the Great Wheel cosmology of the D&D game (see Chapter 5 of the Dungeon Master's Guide). If your campaign uses a different cosmology, you will need to assign different home planes to extraplanar creatures.

Creatures not labeled as extraplanar are natives of the Material Plane, and they gain the extraplanar subtype if they leave the Material Plane. No creature has the extraplanar subtype when it is on a transitive plane; the transitive planes in the D&D cosmology are the Astral Plane, the Ethereal Plane, and the Plane of Shadow.