Wurm, Elder, Storm (CR 23)

Huge Dragon
Alignment: Usually chaotic neutral
Initiative: +4 (Improved Initiative); Senses: keen senses, Listen +26, and Spot +26
Languages: Draconic (although older wurms learn to speak Druidic, Sylvan, and Elven)

AC: 26 (-2 size, +18 natural), touch 8, flat-footed 26
Hit Dice: 20d12+120 (250 hp)
Fort +18, Ref +12, Will +16
Speed: 20 ft., fly 40 ft.(clumsy)
Space: 30 ft./10 ft.
Base Attack +20; Grapple +24
Attack: Bite +31 melee, tail slap +28 melee, 2 claws +28 melee
Full Attack: Bite +31 melee, tail slap +28 melee, 2 claws +28 melee
Damage: Bite 2d8+12, tail slap 1d8+6, claw 1d6+6
Special Attacks/Actions: Breath weapon (cone of stunning lightning 10d6 DC26)
Abilities: Str 34, Dex 19, Con 22, Int 16, Wis 19, Cha 16
Special Qualities: spells (CL 20)
Feats: Cleave; Improved Initiative; Multiattack; Power Attack; Track; Weapon Focus (bite)
Skills: Climb +22*, Hide +7*, Jump +30, Knowledge (nature) +25, Listen +26, Move Silently +18, Spot +26, Survival +22, and Swim +30*
Advancement: Elder wurm 21-27 HD (Huge)
Climate/Terrain: Any land (storms)
Organization: Solitary or pair (1-2)
Treasure/Possessions: Standard

Source: Dragon #296

Breath Weapon: Wurms create special liquids in sacs behind their jaws. Once a wurm uses its breath weapon, it can't use it again for 1d4 rounds. A blast from a breath weapon always leaves from the wurm's mouth and extends in the direction of the wurm's choice. A storm wurm's breath weapon is a cone of stunning lighting (6d6 electricity damage). Creatures in the area must succeed at a Reflex save to take half damage. Any creature damaged by the lightning is also stunned for 1d4 rounds.

Scent (Ex): A storm wurm can detect opponents (even invisible or hidden foes) within 30 feet by sense of smell. Storm wurms can also use this ability to follow tracks by smell. For a full description of this ability, see the Monster Manual.

Improved Grab (Ex): To use this ability, the wurm must hit with its tail slap attack. If it gets a hold, it can constrict.

Constrict (Ex): The wurm can coil around its prey to deal its constriction damage plus tail slap damage with a successful grapple check against any creature of equal size or smaller.

Keen Senses (Ex): Wurms see four times as well as a human in low light conditions and twice as well in normal light. They also have darkvision with a range of 60 feet.

Spells: A wurm knows and casts divine spells as a druid as shown below, gaining bonus spells for a high Wisdom score.

Skills*: Wurms have a natural coloration and limited chameleon ability that grants them a +8 racial bonus to Hide checks in their home environment (a forest wurm in a forest). In addition, wurms with a climb or swim speed receive a +8 racial bonus to Climb or Swim skill checks depending on which movement type they have.