Basilisk, Greater, Abyssal (CR 12)

Large Outsider (Augmented Magical Beast and Extraplanar)
Alignment: Always neutral
Initiative: -1 (Dex); Senses: darkvision 60 ft., low-light vision, Listen +10, and Spot +10

AC: 17 (-1 Dex, -1 size, +9 natural), touch 8, flat-footed 17
Hit Dice: 18d10+90 (189 hp); DR: 10/magic
Fort +18, Ref +12, Will +8
Speed: 20 ft.
Space: 10 ft./5 ft.
Base Attack +18; Grapple +29
Attack: Bite +25 melee
Full Attack: Bite +25 melee
Damage: Bite 2d8+10
Special Attacks/Actions: Petrifying gaze, smite good
Abilities: Str 24, Dex 8, Con 21, Int 3, Wis 10, Cha 15
Special Qualities: SR 23, Resistance to cold 10 and fire 10,
Feats: Alertness; Blind-fight; Great Fortitude; Iron Will; Improved Natural Attack (bite); Lightning Reflexes; Weapon Focus (bite)
Skills: Hide +0*, Listen +10, and Spot +10
Advancement: -
Climate/Terrain: Infinite Layers of the Abyss
Organization: Solitary or colony (3-6)
Treasure/Possessions: None

Source: Monster Manual

The save DC for the abyssal greater basilisk's petrifying gaze (DC 21) is adjusted for its greater Hit Dice and higher Charisma score. An abyssal greater basilisk's natural weapons are treated as magic weapons for the purpose of overcoming damage reduction.

Petrifying Gaze (Su): Turn to stone permanently, range 30 feet; Fortitude negates DC 13.

Smite Good (Su): Once per day an abyssal greater basilisk can make a normal melee attack to deal an extra 18 points of damage against a good foe.

Skills: The basilisk's dull coloration and its ability to remain motionless for long periods of time grant it a +4 racial bonus to Hide checks in natural settings.

Augmented Subtype

A creature receives this subtype whenever something happens to change its original type. Some creatures (those with an inherited template) are born with this subtype; others acquire it when they take on an acquired template. The augmented subtype is always paired with the creature's original type. For example, a wizard's raven familiar is a magical beast (augmented animal). A creature with the augmented subtype usually has the traits of its current type, but the features of its original type. For example, a wizard's raven familiar has an animal's features and the traits of a magical beast.

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.