Dusk Beast (CR 3)

Medium Outsider
Alignment: Usually neutral
Initiative: +6 (+2 Dex, +4 Improved Initiative); Senses: Listen +9 and Spot +13

AC: 15 (+2 Dex, +3 natural), touch 12, flat-footed 13
Hit Dice: 8d8+8 (44 hp)
Fort +7, Ref +8, Will +8
Speed: 30 ft.
Space: 5 ft./10 ft.
Base Attack +8; Grapple +3
Attack: 2 bites +10, tail barb +8
Full Attack: 2 bites +10, tail barb +8
Damage: Bite 1d8+2, tail barb 1d4
Special Attacks/Actions:
Abilities: Str 14, Dex 15, Con 13, Int 8, Wis 15, Cha 13
Special Qualities:
Feats: Combat Reflexes; Improved Initiative; Multiattack
Skills: Climb +11, Hide +17, Listen +9, Move Silently +13, Spot +13, and Survival +9
Advancement: 9-12 HD (Medium-size), 13-18 HD (Large)
Climate/Terrain: Any land and underground
Organization: Solitary or pack (2-5)
Treasure/Possessions: 1/10 coins; 50% goods; 50% items

Source: Manual of the Planes

Skills: Their dark and shadowy nature gives dusk beasts a +4 racial bonus on Hide checks.

Dusk beasts are primarily interested in protecting their shadowed areas - especially if the intruders have light sources. A dusk beast hides in the deepest pool of shadow it can find, then rises suddenly to attack as many foes as it can.

Because it's made of shadowstuff, a dusk beast can extend its necks or tail beyond what seems possible, granting it extended reach. Unwary opponents may find themselves caught in its black teeth when they attempt to skirt it at what they believe to be a safe distance.