Size/Type: Huge Magical Beast (Aquatic)
Hit Dice: 20d10+180 (290 hp)
Speed: Swim 30 ft. (6 squares)
Armor Class: 31 (-2 size, +3 dex, +20 natural)
touch 11, flat-footed 28
Base Attack/Grapple: +20/+40
Attack: Bite +28 melee (2d8+12/19-20)
Full Attack: 2 Bites +28 melee (2d8+12/19-20)
Space/Reach: 15 ft./10 ft.
Special Attacks: Improved grab, constrict 2d6+12, Terrifying Gaze, Breath Weapon
Special Qualities: Darkvision 60 ft., low-light vision, spell-like abilities, fast healing 10
Saves: Fort +21, Ref +15, Will +13
Abilities: Str 34, Dex 17, Con 29, Int 12, Wis 20, Cha 20
Skills: Hide +4, Listen +30, Search +26, Spot +30, Swim +20
Feats: Alertness, Blind-Fight, Combat Expertise, Improved Critical (bite), Improved Initiative, Power Attack, Iron Will
Environment: Temperate aquatic
Challenge Rating: 14
Treasure: Double standard
Alignment: Usually neutral evil
This terrible monster is an enormous, two-headed serpent with a malevolent territorial temperament. It's two heads cooperate when faced with an intruder or threatened but otherwise they will wile away centuries bickering and snapping at each other.
Fen Serpents speak Northtongue, Giant, and Aquan.
Fen serpents like to attack at range employing their attack and breath weapon to excellent effect against opponents who invade their lairs. If pressed into close combat the Fen Serpent will attempt to grapple and crush physically weaker opponents such as typical magic users.
Improved Grab (Ex)
To use this ability, the Fen Serpent must hit with a bite attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and can constrict. The Fen Serpent will often opt to use it's lower body to grapple its foes (taking a -20 penalty to grapple checks)
A fen serpent deals 2d6+12 damage with a successful grapple check.
Breath Weapon (Su)
The Fen Serpent's left head can breath a line of of superheated steam 100 feet long, once every 1d4 rounds, damage 15d6 fire, Reflex DC 29 half; effective both on the surface and underwater. The save DC is Constitution-based.
Terrifying Gaze (Su)
A character meeting the gaze of the Fen Serpent's right head must make a Will save DC 25. If the save fails the character becomes frightened for 2d4 rounds. Otherwise the creature is shaken for 1 round. The save DC is Charisma-based.
A fen serpent has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.