Chwidencha (CR 9)

Large Aberration
Alignment: Always neutral
Initiative: +7 (+3 Dex, +4 Improved Initiative); Senses: darkvision 60 ft., tremorsense 60 ft., Listen +6, and Spot +6
Languages: understand Undercommon, but does not speak it

AC: 21 (-1 size, +3 Dex, +9 natural(, touch 12, flat-footed 18
Hit Dice: 12d8+60 (114 hp)
Fort +11, Ref +9, Will +11
Speed: 30 ft. burrow 30 ft.
Space: 10 ft./5 ft.
Base Attack +9; Grapple +19
Attack: Leg rake +15
Full Attack: 4 leg rakes +15
Damage: Leg rake 1d6+6/19-20
Special Attacks/Actions: Constrict 3d6+9, improved grab
Abilities: Str 22, Dex 17, Con 20, Int 3, Wis 16, Cha 3
Special Qualities: leg regeneration, sonic vulnerability
Feats: Great Fortitude; Improved Critical (leg rake); Improved Initiative; Lightning Reflexes; Weapon Focus (leg rake)
Skills: Climb +9, Hide +3, Listen +6, Move Silently +6, and Spot +6
Advancement: 13-18 HD (Large); 19-36 HD (Huge)
Climate/Terrain: Any underground
Organization: Solitary, cluster (2-5), or colony (11-20)
Treasure/Possessions: -

Source: Fiend Folio
Drow of the Underdark

Constrict (Ex): With a successful grapple check, a chwidencha can crush a grabbed opponent, dealing 3d6+9 points of bludgeoning damage.

Improved Grab (Ex): If a chwidencha hits an opponent that is at least one size category smaller than itself with at least two leg rake attacks, it deals normal damage and attempts to starr a grapple as a free action without provoking an attack of opportunity (grapple bonus +19). If it gets a hold, it also constricts on the same round. Thereafter, the chwidencha has the option to conduct the grapple normally, or simply use its legs to hold the opponent (-20 penalty on grapple check, but the chwidencha is not considered grappled). In either case, each successful grapple check it makes during successive rounds automatically deals rake and constrict damage.

Leg Regeneration (Ex): Foes can attack a chwidencha's legs, but only when those appendages are actually holding an opponent. A leg has an AC of 19 (touch 12) and can withstand 20 points of damage. The loss of a leg does not harm the creature (that is, the damage does not apply against its hit point total), and the chwidencha regrows the limb within a day.

Tremorsense (Ex): A chwidencha can automatically sense the location of anything within 60 feet that is in contact with the ground.

A chwidencha lurks in the darkness and uses its tremorsense to notify it of approaching prey. It usually hides beneath a layer of earth, then crawls out and grapples an opponent. It takes several hours for a chwidencha to devour its victim, so it usually drags the body off to some safe place to consume it.