Shadow Mastiff (CR 5)

Medium Outsider (Extraplanar)
Alignment: Always neutral evil
Initiative: +5 (+1 Dex, +4 Improved Initiative); Senses: darkvision 60 ft., scent, Listen +8, and Spot +8

AC: 14 (+1 Dex, +3 natural), touch 11, flat-footed 13
Hit Dice: 4d8+12 (30 hp)
Fort +7, Ref +5, Will +5
Speed: 50 ft.
Space: 5 ft./5 ft.
Base Attack +4; Grapple +7
Attack: Bite +7 melee
Full Attack: Bite +7 melee
Damage: Bite 1d6+4
Special Attacks/Actions: Bay, trip
Abilities: Str 17, Dex 13, Con 17, Int 4, Wis 12, Cha 13
Special Qualities: Shadow blend
Feats: Dodge; Improved Initiative; Track
Skills: Hide +8, Listen +8, Move Silently +8, Spot +8, and Survival +8*
Advancement: 5-6 HD (Medium-size); 7-12 HD (Large)
Climate/Terrain: Plane of Shadow
Organization: Solitary, pair, or pack (5-12)
Treasure: None

Source: Monster Manual

Bay (Su): When a shadow mastiff howls or barks, all creatures except evil outsiders within a 300-foot spread must succeed at a Will save (DC 13) or become panicked for 2d4 rounds. This is a sonic, mind-affecting fear effect. Whether or not the save is successful, an affected creature is immune to that mastiff's bay for one day.

Trip (Ex): A shadow mastiff that hits with its bite attack can attempt to trip the opponent as a free action (see page 139 in the Player's Handbook) without making a touch attack or provoking an attack of opportunity. If the attempt fails, the opponent cannot react to trip the shadow mastiff.

Shadow Blend (Su): During any conditions other than full daylight, a shadow mastiff can disappear into the shadows, giving it nine-tenths concealment. Artificial illumination, even a light or continual flame spell, does not negate this ability. A daylight spell, however, will.

Skills: A shadow mastiff receives a +4 racial bonus to Survival checks when tracking by scent.

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.