Mastyrial (CR 8)

Large Animal
Alignment: Always neutral
Initiative: +0; Senses: low-light vision, tremorsense, Listen +7, and Spot +7

AC: 22 (-1 size, +13 natural), touch 9, flat-footed 22
Hit Dice: 12d8+48 (102 hp)
Fort +12, Ref +8, Will +4
Speed: 30 ft., burrow 15 ft.
Space: 10 ft./5 ft.
Base Attack +9; Grapple +9
Attack: Claw +14 melee
Full Attack: 2 claws +14 melee and bite +9 melee and tail +9 melee
Damage: claw 1d8+6, bite 1d8+3, tail 1d6+3 plus poison
Special Attacks/Actions: Poison, rend 2d6+9
Abilities: Str 22, Dex 11, Con 14, Int 2, Wis 10, Cha 7
Special Qualities:
Feats: Alertness; Power Attack
Skills: Listen +7, Move Silently +5, and Spot +7
Advancement: 13-24 HD (Large); 25-36 HD (Huge)
Climate/Terrain: Warm deserts (Athas)
Organization: Solitary or pair
Treasure/Possessions: None

Source: Dungeon #111

Rend (Ex): A mastyrial that hits with both claw attacks latches onto the opponent's body and tears the flesh. This attack automatically deals an extra 2d6+9 points of damage.

Poison (Ex): A mastyrial's tail stinger has a venom that is mildly paralytic and gives its victims muscle tremors. It deals initial and secondary damage of 1d8 Dex (Fort DC 20 negates). The save DC is Constitution-based.

Mastyrials are unsubtle creatures, simply wading into melee to make a full attack as often as possible.