Root of All Evil (CR 8)

Huge Plant
Alignment: Always neutral evil
Initiative: -1 (Dex); Senses: tremorsense, Listen +13, and Spot +13

AC: 20 (-2 size, -1 Dex, +13 natural), touch 7, flat-footed 20
Hit Dice: 13d8+65 (123 hp); DR: 10/good
Fort +13, Ref +5, Will +4
Speed: 20 ft., burrow 30 ft.
Space: 10 ft./10 ft.
Base Attack +9; Grapple +13
Attack: Bite +17 melee
Full Attack: Bite +17 melee
Damage: Bite 2d6+13 and 2d6 unholy/19-20
Special Attacks/Actions: Improved grab, swallow whole, smite good
Abilities: Str 28, Dex 9, Con 21, Int 7, Wis 11, Cha 10
Special Qualities: Blood scent, magic circle against good, plant traits, SR 19, unholy bite
Feats: Improved Critical (bite); Lightning Reflexes; Weapon Focus (bite)
Skills: Hide +4, Listen +13, and Spot +13
Advancement: 14-16 HD (Huge); 17-32 HD (Gargantuan); 32-48 HD (Colossal)
Climate/Terrain: Any land
Organization: Solitary
Treasure: None

Source: Web

Roots of all evil hate life and seek to kill all living, blood-bearing beings that they encounter. Odd in appearance, a root of all evil resembles a large parsnip with a vicious maw surrounded by green, ferny foliage like the top. A root of all evil feeds primarily on blood, but also needs at least two hours of sunlight per week.

Roots of all evil are never found with others of their kind. However, undead often form a happenstance symbiotic partnership with the plant by inhabiting areas frequented by a root of all evil. They benefit from the root's magic circle against good and the root benefits from the undead's occasional flanking and additional attacks, especially when attacking a group of living creatures.