Harpy (CR 4)

Medium Monstrous Humanoid
Alignment: Usually chaotic evil
Initiative: +2 (Dex); Senses: darkvision 60 ft., Listen +7, and Spot +3

AC: 13 (+2 Dex, +1 natural), touch 12, flat-footed 11
Hit Dice: 7d8 (31 hp)
Fort +2, Ref +7, Will +6
Speed: 20 ft., fly 80 ft. (average)
Space: 5 ft./5 ft.
Base Attack +7; Grapple +7
Attack: Club +7 melee
Full Attack: Club +7/+2 melee, and 2 claws +2 melee
Damage: Club 1d6, claw 1d3
Special Attacks/Actions: Captivating song
Abilities: Str 10, Dex 15, Con 10, Int 7, Wis 10, Cha 17
Special Qualities:
Feats: Dodge; Flyby Attack; Persuasive
Skills: Bluff +11, Intimidate +7, Listen +7, Perform (oratory) +5, and Spot +3
Advancement: By character class
Climate/Terrain: Temperate marshes
Organization: Solitary, pair or flight (7-12)
Treasure/Possessions: Standard

Source: Monster Manual

Captivating Song (Su): The most insidious ability of the harpy is its song. When a harpy sings, all creatures (other than harpies) within a 300-foot spread must succeed at a Will save (DC 15) or become utterly captivated. This is a sonic, mind-affecting charm. If the save is successful, that creature cannot be affected again by that harpy's song for one day.

A captivated victim walks toward the harpy, taking the most direct route available. If the path leads into a dangerous area (through flame, off a cliff, etc.), that creature gets a second saving throw. Captivated creatures can take no actions other than to defend themselves. (Thus, a fighter cannot run away or attack but suffers no defensive penalties.) A victim within 5 feet of the harpy stands there and offers no resistance to the monster's attacks. The effect continues for as long as the harpy sings. A bard's countersong ability allows the captivated creature to attempt a new Will save.

When a harpy engages in battle, it prefers to use Flyby Attack and strike with a melee weapon.