Thunder Worm (CR 21)

Colossal Magical Beast (Incorporeal)
Alignment: Always neutral
Initiative: +9 (+5 Dex, +4 Improved Initiative); Senses: blindsight 90 ft., darkvision 60 ft., low-light vision, Listen +47, and Spot +47

AC: 23 (-8 size, +5 Dex, +16 deflection), touch 23, flat-footed 18
Hit Dice: 48d10+432 (696 hp)
Fort +37, Ref +33, Will +22
Speed: Fly 60 ft. (perfect)
Space: 40 ft./15 ft.
Base Attack +46; Grapple -
Attack: Incorporeal touch +46 melee
Full Attack: Incorporeal touch +46 melee
Damage: Incorporeal touch 4d6 electricity plus 4d6 sonic
Special Attacks/Actions: Engulf, thunderclap
Abilities: Str -, Dex 21, Con 28, Int 14, Wis 19, Cha 42
Special Qualities: defensive shock, electricity immunity, incorporeal subtype, sonic immunity, SR 30
Feats: Alertness; Blind-fight; Combat Expertise; Combat Reflexes; Dodge; Endurance; Great Fortitude; Improved Initiative; Iron Will; Lightning Reflexes; Mobility; Run; Spring Attack; Skill Focus (Hide); Track; Weapon Focus (incorporeal touch); Whirlwind Attack
Skills: Hide +33, Listen +47, Search +42, Spot +47, and Survival +45
Advancement: 49-144 HD (Colossal)
Climate/Terrain: Temperate land
Organization: Solitary or pod (2-4)
Treasure/Possessions: -

Source: Fiend Folio

Engulf (Ex): As an incorporeal creature, a thunder worm can position itself so that it occupies the same spaces as its enemies - a fate potentially far worse than being swallowed by a purple worm. This attack affects as many creatures as will fit within the cloud worm's facing (a 40-foot cube). Target creatures must make a successful Reflex save (DC 43) or take electricity and sonic damage as if hit by the cloud worm's incorporeal touch attack. Creatures that fail their saving throws take damage each round that they remain within the cloud worm's body, with no further opportunities for saving throws. Creatures that make a successful saving throw must continue to save each round that they remain within the worm's body, taking damage if they fail (and thereafter receiving no additional saving throws until they move out of its body).

Thunderclap (Ex): A thunder worm can produce a thunderous boom as a standard action. Creatures within 30 feet of the worm must make a Reflex save (DC 43) or take 24d8 points of sonic damage. After producing a thunderclap, a thunder worm must wait 1d4 rounds before doing it again.

Blindsight (Ex): A thunder worm maneuvers and fights not only by sight, but also by using hearing and smell to ascertain its surroundings. This ability enables it to discern objects and creatures within 90 feet. A thunder worm usually does not need to make Spot or Listen checks to notice creatures within range of its blindsight.

Defensive Shock (Ex): An opponent that uses a metal melee weapon or a natural weapon to deal damage to a thunder worm must make a Reflex save (DC 34) or take 2d6 points of electricity damage from the creature's body.

Incorporeal Subtype: A thunder worm can be harmed only by other incorporeal creatures, +1 or better magic weapons, spells, spell-like abilities, and supernatural abilities. The creature has a 50% chance to ignore any damage from a corporeal source, except for force effects or attacks made with ghost touch weapons. A thunder worm can pass through solid objects but not force effects, at will. Its attacks ignore natural armor, armor, and shields, but deflection bonuses and force effects work normally against it. A thunder worm always moves silently and cannot be heard with Listen checks if it doesn't wish to be.

A thunder worm tends to initiate combat with its thunder clap attack; then it closes on its foes to touch and engulf them.

Incorporeal Subtype

Some creatures are incorporeal by nature, while others (such as those that become ghosts) can acquire the incorporeal subtype. An incorporeal creature has no physical body. It can be harmed only by other incorporeal creatures, magic weapons or creatures that strike as magic weapons, and spells, spell-like abilities, or supernatural abilities. It has immunity to all nonmagical attack forms. Even when hit by spells, including touch spells or magic weapons, it has a 50% chance to ignore any damage from a corporeal source (except for positive energy, negative energy, force effects such as magic missile, or attacks made with ghost touch weapons). Non-damaging spell attacks affect incorporeal creatures normally unless they require corporeal targets to function (such as the spell implosion) or they create a corporeal effect that incorporeal creatures would normally ignore (such as a web or wall of stone spell). Although it is not a magical attack, a hit with holy water has a 50% chance of affecting an incorporeal undead creature.

An incorporeal creature's natural weapons affect both in incorporeal and corporeal targets, and pass through (ignore) corporeal natural armor, armor, and shields, although deflection bonuses and force effects (such as mage armor) work normally against it. Attacks made by an incorporeal creature with a nonmagical melee weapon have no effect on corporeal targets, and any melee attack an incorporeal creature makes with a magic weapon against a corporeal target has a 50% miss chance except for attacks it makes with a ghost touch weapon, which are made normally (no miss chance).

Any equipment worn or carried by an incorporeal creature is also incorporeal as long as it remains in the creature's possession. An object that the creature relinquishes loses its incorporeal quality (and the creature loses the ability to manipulate the object). If an incorporeal creature uses a thrown weapon or a ranged weapon, the projectile becomes corporeal as soon as it is fired and can affect a corporeal target normally (no miss chance). Magic items possessed by an incorporeal creature work normally with respect to their effects on the creature or another target. Similarly, spells cast by an incorporeal creature affect corporeal creatures normally.

An incorporeal creature has no natural armor bonus but has a deflection bonus equal to its Charisma bonus (always at least +1, even if the creature's Charisma score does not normally provide a bonus).

An incorporeal creature can enter or pass through solid object but must remain adjacent to the object's exterior, and so cannot pass entirely through an object whose space is larger than its own. It can sense the presence of creatures or objects a square adjacent to its current location, but enemies have total concealment from an incorporeal creature that is inside an object. In order to see clearly and attack normally, a incorporeal creature must emerge. An incorporeal creature inside an object has total cover, but when it attacks a creature outside the object it only has cover, so a creature outside with a readied action could strike at it as it attacks. An incorporeal creature cannot pass through a force effect.

Incorporeal creatures pass through and operate in water as easily as they do in air. Incorporeal creatures cannot fall or take falling damage. Incorporeal creature cannot make trip or grapple attacks against corporeal creatures, nor can they be tripped or grappled by such creatures. In fact, they cannot take any physical action that would move or manipulate a corporeal being or its equipment, nor are they subject to such actions. Incorporeal creatures have no weight and do not set off traps that are triggered by weight.

An incorporeal creature moves silently and cannot be heard with Listen checks if it doesn't wish to be. It has no Strength score, so its Dexterity modifier applies to both its melee attacks and its ranged attacks. Non-visual senses, such as scent and blindsight, are either ineffective or only partly effective with regard to incorporeal creatures. Incorporeal creatures have an innate sense of direction and can move at full speed even when they cannot see.