Hell Louse (CR 3)

Large Vermin (Extraplanar and Fiendish)
Alignment: Lawful Evil
Initiative: +2(Dex); Senses: darkvision 60 ft, low-light vision, and Spot +5

AC: 15 (-1 size, +2 Dex, +4 natural), touch 11, flat-footed 13
Hit Dice: 6d8+9 (36 hp); DR: 5/magic
Fort +6, Ref +4, Will +2
Speed: 30 ft. and Climb 30 ft.
Space: 10 ft./10 ft.
Base Attack +4; Grapple +11
Attack: Melee: bite +7
Damage: Bite 2d6+4 plus poison
Special Attacks/Actions:
Attack Options: poison (injury, Fortitude DC 14, 1d6 Dex/1d6 Dex), smite good 1/day (+6 damage)
Abilities: Str 17, Dex 15, Con 12, Int 3, Wis 10, Cha 2
Special Qualities: Immune to mind-affecting spells and abilities; Resist fire 5, cold 5; Vermin traits
Feats: Improved Natural Attack (bite), Toughness, Weapon Focus (bite),
Skills: Move Silently +6 and Spot +5
Advancement: -
Climate/Terrain: Malbolge (6th layer of Baator)
Organization: Solitary
Treasure/Possessions: -

Source: Fiendish Codex II

Smite Good (Su): Once per day, can make a normal melee attack to deal +6 damage against a good foe.

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.