Night Twist, Ancient (CR 20)

Huge Plant
Alignment: Always neutral evil
Initiative: -2 (Dex); Senses: low-light vision, Listen +17, and Spot +18

AC: 38 (-2 size, -2 Dex, +26 natural, +6 deflection), touch 12, flat-footed 38
Hit Dice: 25d8+300 (412 hp); DR: 15/slashing
Fort +32, Ref +12, Will +19
Speed: 10 ft.
Space: 15 ft./25 ft.
Base Attack +18; Grapple +43
Attack: Slam +33 melee
Full Attack: 6 slams +33 melee
Damage: Slam 4d6+17
Special Attacks/Actions: Death curse, despair song, spell-like abilities, wind blast
Abilities: Str 45, Dex 6, Con 34, Int 12, Wis 16, Cha 23
Special Qualities: plant traits, unholy grace, vulnerability to fire
Feats: Blind-fight; Diehard; Endurance; Improved Natural Armor (3); Improved Sunder; Iron Will; Power Attack
Skills: Hide +60, Knowledge (nature) +18, Listen +17, Move Silently +8, and Spot +18
Advancement: 26-48 HD (Huge)
Climate/Terrain: Temperate marshes
Organization: Solitary
Treasure: Standard coins, no goods, standard items

Source: Monster Manual III

Night twists live for an indefinite length of time. Some legends claim the age of the most ancient specimens can be counted in millennia. Feeding off the despair, fear, and corpses of victims over hundreds of centuries and growing to a height of 30 feet or more, an ancient night twists is a horrifying and daunting spectacle to mortals. Each one weighs some 4,500 pounds and speaks Common, Elven, and Sylvan.