Stone Flyer (CR 3)

Large Magical Beast (Earth and Extraplanar)
Alignment: Usually neutral evil
Initiative: +1 (Dex); Senses: darkvision 60 ft., low-light vision, tremorsense, Listen +6, and Spot +6

AC: 16 (-1 size, +1 Dex, +6 natural), touch 10, flat-footed 15
Hit Dice: 5d10+15 (42 hp); DR: 5/bludgeoning
Fort +7, Ref +5, Will +1
Speed: 50 ft., fly 60 ft. (average)
Space: 10 ft./5 ft.
Base Attack +5; Grapple +14
Attack: Bite +10 melee (1d8+7)
Full Attack: Bite +10 melee (1d8+7)
Damage: -
Special Attacks/Actions:
Abilities: Str 21, Dex 13, Con 16, Int 5, Wis 10, Cha 8
Special Qualities: earth glide, earth glide rider, SR 13
Feats: Alertness; Weapon Focus (bite)
Skills: Listen +6 and Spot +6
Advancement: 6-10 HD (Large)
Climate/Terrain: Underground
Organization: Solitary, pair, or pack (5-10)
Treasure/Possessions: Standard

Source: Underdark

Earth Glide (Ex): A stone flyer can glide through stone, dirt, or almost any other sort of earth except metal as easily as a fish swims through water. Its burrowing leaves behind no tunnel or hole, and its passage does not create any ripples or other signs of its presence. A move earth spell cast on an area the stone flyer occupies pushes it back 30 feet but has no other effect.

Earth Glide Rider (Su): A stone flyer can extend its earth glide ability to include a rider and gear, up to a medium load.

Tremorsense (Ex): A stone flyer can automatically sense the location of any creature or object within 60 feet that is in contact with the ground.

Stone flyers usually hunt prey in packs, working in concert to bring down creatures that are traveling alone or lagging behind in a group. Once their quarry is unconscious or dead, they retreat into the earth or stone, taking their prey along to be consumed in safety, away from the site of the kill.

Earth Subtype

This subtype usually is used for elementals and outsiders with a connection to the Elemental Plane of Earth. Earth creatures usually have burrow speeds, and most earth creatures can burrow through solid rock.

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.