Siren: A powerful sorceress who uses the power of her songs to bend the minds and hearts of those around her, and she is full of useful skills and information from her time spent among social circles.
Sirens have many Charisma-based skills (6 + Int), and all their magic is based on Charisma as well, and medium base attack. They spontaneously sing spellsongs, which always have verbal components and can produce powerful enchantment effects at lower levels than most classes (For instance, Sirens get Hideous Laughter at level 1).
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Amazon: A skillful, stealthy, and mighty warrior-maiden known for using her natural surroundings to her advantage. They live in the jungles far from Seelyne
Runemaiden/Runetemptress- A mighty warrior devoted to the arcane mysteries of Amaranthia, she draws runes to invoke her powers, and others can use them as well
Amazons gets feats, full attack bonus, plenty of skills (6 + Int bonus), and a variety of useful combat-related abilities. You can see Antiope, the iconic Amazon, fighting Araneau, the iconic Swashbuckler, in the Swashbuckler entry of the Encyclopaedia Altanica.
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Runemaiden/Runetemptress: A mighty warrior devoted to the arcane mysteries of Amaranthia, she draws runes to invoke her powers, and others can use them as well
Runemaidens have full base attack bonus, but not many skills (2 + Int mod). They do, however, gain a variety of runes and rune-based special abilities. Mainly, the runes allow her to put her spells per day into one use magic items that anyone can use, allowing her to, for instance distribute a Cat's Grace rune to the party Swashbuckler so he can activate it himself. If somebody else uses them, though, they are less effective than if she uses them herself.
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Votress: A holy maiden devoted to one of the fey lords, often Titania; she forswears the use of weapons and perfects her mind and body in her mistress's service
Votresses gain divine magic (as a cleric) and several special abilities from their vows to their mistress. They have medium base attack and a fairly nice skill pool (with 4 + Int skills). They can't use or carry weapons, or they lose their powers.
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Nymph: Not to say that Naiads, Dryads, Oreads, Haliai, Oceanids, Nereids, Meliai, Epimeliads, Daphniai, Aurai, Anthousa, Lampiads, etc cannot take other classes, but this class embodies the spirit of the nymph. Members are skillful and emphasise their ties to nature, while simultaneously gaining powers associated with the Monster Manual nymph.
Nymphs have medium base attack and maxed out skills with a large selection (8 + Int mod), and special abilities associated with nymphs. Not to mention the druid spellcasting. Since the Monster Manual Nymph is a Naiad, taking levels in the Nymph class as a Naiad produces a similar (but more interesting and balanced) result to playing a Monster Manual Nymph, although each Nymph type has her own special differences with this class. Think of these as Racial or Evolved levels for Nymphs, since Sidhe can't take this class. There's still 20 levels though.
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Swanmay: The warrior-maidens of Seelyne, who are known for their love of animals; they can even transform into swan form.
Swanmays have full base attack bonus, feats, and druid magic, with a decent skill pool and skills (4 + Int bonus). They also like to play with their animal friends, turn into animals (and magic swans), and summon animals.