Troll, Crystalline (CR 7)

Large Giant
Alignment: Usually chaotic evil
Initiative: +2 (Dex); Senses: darkvision 60 ft., low-light vision, scent, Listen +7, and Spot +8

AC: 18 (-1 size, +2 Dex, +7 natural), touch 11, flat-footed 16
Hit Dice: 10d8+60 (105 hp)
Fort +13, Ref +5, Will +4
Speed: 30 ft.
Space: 10 ft./10 ft.
Base Attack +7; Grapple +17
Attack: Claw +12 melee
Full Attack: 2 claws +12 melee and bite +7 melee
Damage: Claw 1d6+6, bite 1d6+3
Special Attacks/Actions: Rend 2d6+9
Abilities: Str 23, Dex 14, Con 23, Int 6, Wis 9, Cha 8
Special Qualities: immunity to acid, regeneration 5, vulnerability to sonic
Feats: Alertness; Iron Will; Power Attack; Track
Skills: Listen +7 and Spot +8
Advancement: By character class
Climate/Terrain: Temperate mountains
Organization: Solitary or gang (2-5)
Treasure/Possessions: Standard

Source: Monster Manual III

Rend (Ex): If a crystalline troll hits with both claw attacks, it latches onto the opponent's body and tears the flesh. This attack automatically deals an additional 2d6+9 points of damage.

Regeneration (Ex): Sonic attacks deal normal damage to a crystalline troll. If a crystalline troll loses a limb or body part, the lost portion regrows in 3d6 minutes. The creature can reattach the severed member instantly by holding it to the stump.

Like an ordinary troll, a crystalline troll has no fear of death and joins combat with vigor and pleasure. It attacks the nearest opponent. Even when being hurt with sonic attacks, the troll will continue its assault.