Rokurokubi
The comely geisha waves her fan coyly- and then extends what turns out to be a fang-filled maw on the end of a serpentine, monstrous neck!

Rokurokubi (CR 5; XP 1,600)
LE Medium monstrous humanoid
Init +3; Senses darkvision 60 ft.; Perception +0
Defense
AC 14, touch 14, flat-footed 11
(+1 armor, +3 Dex)
hp 52 (8d10+8)
Fort +3, Ref +9, Will +6
DR 5/—; Immune decapitation
Offense
Speed 30 ft.
Melee bite +11 (1d4+2 plus draw blood), fighting fan +5 (1d4/x3)
Space 5 ft.; Reach 5 ft. (40 ft. with bite)
Special Attacks draw blood, fearful presence (W-DC 16), lulling song (W-DC 16)
Statistics
Str 15, Dex 16, Con 12, Int 12, Wis 10, Cha 14
Base Atk +8; CMB +10; CMD 23
Feats Skill Focus (Bluff, Disguise, Perform [sing]), Weapon Focus (bite)
Skills Bluff +13, Disguise +13, Perform (sing) +13, Sense Motive +8, Stealth +14
Ecology
Environment ruins, urban
Organization solitary
Treasure double
Special Abilities
Draw Blood (Ex) With a successful bite attack, the rokurokubi deals 1d4 points of Constitution damage.
Fearful Presence (Su) As a move action, the rokurokubi can transform her face into a horrific demonic visage. All within 30 ft. who can see the rokurokubi must make a Will save (DC 16) or become shaken for 2d6 rounds. A creature that makes its save is immune to the rokurokubi’s fearsome presence for 24 hours. This is a fear effect and the save DC is Charisma-based.
Lulling Song (Su) When a rokurokubi sings its enchanting song of loss, all living creatures within 60 ft. must make a successful Will save (DC 16) or be affected by either charm person or sleep, as if cast by a 8th level sorcerer. This is a sonic, mind-affecting charm effect. Any creature who successfully resists the rokurokubi’s song cannot be affected again by the same lulling song for 24 hours.

Though thought by some to be a supernatural devil or demon, the ghastly rokurokubi is a powerful hag-like being of solitary nature, who feeds on the unwary and the gullible, and is capable of infiltrating human society rather easily. Rokurokubi prey on humans and those that associate with them for food and treasure, as they like to live in comfort, sometimes even maintaining elegant houses, if they have fooled the local populace enough. They reproduce with human and near-human men they can seduce, producing immature rokurokubi- though sometimes they take an ogre-mage as a mate, giving some credence to their existence as some kind of female form of that advanced ogre race.

On Porphyra
Rokurokubi traveled, concealed, with the Landed populace of The Lotus Blossom Steppes. They made contact early on with the half-rakshasa forces there but were greatly diminished with their defeat though they sometimes spread south, or help oni agents who reward them well.