Ice Serpent (CR 3)

Large Elemental (Air and Cold)
Alignment: Always neutral
Initiative: +7 (Dex); Senses: Spot +6

AC: 16 (-1 size, +7 Dex), touch 16, flat-footed 9
Hit Dice: 6d8+18 (45 hp); DR: 5/magic
Fort +5, Ref +12, Will +13
Speed: 80 ft.
Space: 10 ft./5 ft.
Base Attack +4; Grapple +13
Attack: Constrict +8 melee
Full Attack: Constrict +8 melee
Damage: Constrict 1d8+7 plus cold
Special Attacks/Actions: Constrict
Abilities: Str 20, Dex 25, Con 16, Int 4, Wis 13, Cha 11
Special Qualities: Elemental immunities, cold subtype
Feats: Dodge; Mobility; Power Attack
Skills: Move Silently +11 and Spot +6
Advancement: 7-9 HD (Large); 10-18 HD (Huge)
Climate/Terrain: Cold plains
Organization: Solitary
Treasure/Possessions: None

Source: Monster Compendium: Monsters of Faerûn

Constrict (Ex): When an ice serpent hits an opponent with its body, it makes a free grapple check (without provoking an attack of opportunity) in addition to dealing damage. If the serpent wins this check, it wraps itself around the opponent and begins to deal 2d4 points of subdual damage through the numbing cold of its body. If the victim falls unconscious from the subdual damage, the ice serpent begins to deal normal damage at the same rate.

Cold Subtype (Ex): Cold immunity; double damage from fire except on a successful save.

Ice serpents feed upon the heat of living creatures. Like a constrictor snake, they wrap themselves around their prey - but rather than squeezing the victim to death, they drain the heat from the creatures body.

Air Subtype

This subtype usually is used for elementals and outsiders with a connection to the Elemental Plane Air. Air creatures always have fly speeds and usually have perfect maneuverability (see the section on Movement).

Cold Subtype

A creature with the cold subtype has immunity to cold. It has vulnerability to fire, which means it takes half again as much (+50%) damage as normal from fire, regardless of whether a saving throw is allowed, or if the save is a success or failure.