Displacer Beast (Serpent) (CR 2)

Medium Magical Beast
Alignment: Usually chaotic evil
Initiative: +1 (Dex); Senses: darkvision 60 fix, low-light vision, and Listen +6

AC: 13 (+1 Dex, +2 natural), touch 11, flat-footed 12
Hit Dice: 2d10+8 (19 hp)
Fort +7, Ref +4, Will +3
Speed: 20 ft., climb 10 ft., swim 10 ft.
Space: 5 ft./5 ft.
Base Attack +2; Grapple +5
Attack: Bite +5 melee
Full Attack: Bite +5 melee
Damage: Bite 1d6+4
Special Attacks/Actions: -
Abilities: Str 17, Dex 12, Con 19, Int 5, Wis 12, Cha 2
Special Qualities: displacement
Feats: Iron Will
Skills: Climb +11, Listen +6, and Swim +11
Advancement: 3-5 HD (Medium); 6 HD (Large)
Climate/Terrain: Warm forests
Organization: Solitary pair, brood (2-7 plus 0, 1, or 2 leaders with 4 HD)
Treasure/Possessions: 50% coins; triple goods, 50% items

Source: Miniatures Handbook

Displacement (Su): light-bending glamer continually surrounds a displacer serpent, making it difficult to surmise the creature's true location. Any melee or ranged attack directed at it has a 50% miss chance unless the attacker can locate the serpent by some means other than sight. A true seeing effect allows the user to see the serpent's position, but see invisibility has no effect.

Skills: A displacer serpent has a +8 racial bonus on Climb checks and can always choose to take 10 on Climb checks, even if rushed or threatened. It also 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.

Displacer serpents are unexceptional in their tactics, lashing out when hungry or bored, slithering away when hurt or scared.