Landwyrm, Desert (CR 18)

Gargantuan Dragon
Alignment: Usually neutral evil
Initiative: +4; Senses: Listen +34 and Spot +38*
Languages: Draconic and Common

AC: 33 (-4 size, +27 natural), touch 6, flat-footed 33
Hit Dice: 32d12+224 (432 hp)
Fort +25, Ref +18, Will +21
Speed: 40 ft., burrow 20 ft.
Space: 20 ft./15 ft.
Base Attack +32; Grapple +56
Attack: Bite +40 melee
Full Attack: Bite +40 melee and 2 claws +38 melee
Damage: Bite 4d6+12/19-20, claw 2d8+6
Special Attacks/Actions: Frightful presence, sandstorm
Abilities: Str 35, Dex 10, Con 24, Int 21, Wis 17, Cha 20
Special Qualities: Desert adaptation
Feats: Alertness; Blind-fight; Cleave; Great Cleave; Improved Critical (bite); Improved Initiative; Improved Overrun; Multiattack; Power Attack; Stealthy; Track
Skills: Bluff +35, Concentration +37, Diplomacy +39, Escape Artist +30, Gather Information +7, Hide +20*, Intimidate +7, Knowledge (arcana) +35, Knowledge (local) +35, Knowledge (nature) +35, Listen +34, Move Silently +31, Sense Motive +31, Spot +38*, and Survival +32
Advancement: 33-39 HD (Gargantuan); 40-48 HD (Colossal)
Climate/Terrain: Warm deserts
Organization: Solitary, pair, or flight (3-6)
Treasure/Possessions: Standard

Source: Draconomicon

Desert Adaptation (Ex): Desert landwyrms can go without water for a number of days equal to their Constitution score. Even after this point, they need only make a Constitution check each day (rather than each hour, as noted in Starvation and Thirst) to avoid taking nonlethal damage from thirst. They take no nonlethal damage from heat exposure (though they take damage from fire normally). They suffer no ill effects from being caught in dust storms or sandstorms (including their own sandstorm attack; see below).

Frightful Presence (Ex): 160-ft. radius, HD 31 or fewer, Will DC 31 negates.

Sandstorm (Ex): As a standard action, a desert landwyrm can create a small sandstorm by kicking up sand, dust, and debris in a 120-foot-radius spread centered on itself. Any creature in the affected area must succeed on a DC 33 Fortitude save or be blinded for 1d6 rounds. This ability only functions in deserts or areas with similar quantities of dust or sand.

Skills: Desert landwyrms have a +4 racial bonus on Spot checks. *They have a +4 racial bonus on Hide checks when in temperate or warm desert environments. This bonus on Hide checks increases to +8 when the landwyrm is immobile.