Drake, Rage, Fiendish (CR 13)

Large Dragon
Alignment: Usually chaotic evil
Initiative: +7 (+3 Dex, +4 Improved Initiative); Senses: blindsense 30 ft., darkvision 60 ft., low-light vision, Listen +19, and Spot +19
Languages: Does not speak, understands limited Draconic and Common

AC: 20 (-1 size, +3 Dex, +8 natural), touch 12, flat-footed 17
Hit Dice: 21d12+147 plus 21 (304 hp); DR: 10/magic
Fort +19, Ref +15, Will +13
Speed: 60 ft.
Space: 10 ft./5 ft.
Base Attack +21; Grapple +34
Attack: Claw +20 melee*
Full Attack: 2 claws +20 melee* and bite +15 melee*
Damage: Claws 1d8+18/19-20*, bite 2d6+13* (*Includes adjustments for Power Attack feat.)
Special Attacks/Actions: Improved grab, pounce, rage, rake, smite good, worry
Abilities: Str 28, Dex 17, Con 24, Int 4, Wis 12, Cha 10
Special Qualities: immunity to sleep, and paralysis, resistance to cold 10 and fire 10, SR 26
Feats: Cleave; Great Cleave; Improved Critical (claw); Improved Initiative; Improved Natural Attack (claw); Improved Natural Attack (bite); Improved Toughness; Power Attack
Skills: Hide +14, Jump +36, Listen +19, Move Silently +17, and Spot +19
Advancement: 22-28 HD (large); 29-42 HD (Huge)
Climate/Terrain: Cold forests
Organization: Solitary or pair
Treasure/Possessions: None

Source: Monster Manual III

A fiendish rage drake normally attacks using its Power Attack feat, taking a -9 penalty on its attack rolls and gaining a +9 bonus on damage rolls.

Rage (Ex): Four times per day, a fiendish rage drake can enter a state of fierce rage that lasts 12 rounds. The following changes are in effect as long as he rages: AC 18 (touch 10, flat-footed 15); hp increase by 42; Ark +22 melee (1d8+20/19-20, claw); Full Atk +22 melee (1d8+20/19-20, 2 claws) and +14 melee (2d6+15, bite); SV Fort +21, Will +15; Str 32, Con 28.; Jump +38. Unlike a barbarian, however, a fiendish rage drake is not fatigued after raging. A rage drake can end its rage early, though it seldom does so even when all its foes are apparently defeated.

Smite Good (Su): Once per day, a fiendish rage drake can make a normal melee attack to deal an extra 20 points of damage against a good foe.