Nagaina's story:
A wide-shouldered, narrow-waisted woman, Nagaina is slender and graceful. Her dark eyes are huge, filling nearly half her face, and are framed with long lashes that lend her countenance a smoldering intensity. Her skin is dark, almost blue-black, and she wears her startling golden hair in a single long braid that hangs down her back. She dresses in dark purple leather and midnight blue silk. A fine network of tribal scars runs across her face, underscoring her mesmerizing eyes and high cheekbones.
Nagaina was born into a tribe of draconically descended humans who worshiped the serpent lords. Once a year her people would make their way into the steaming jungles to the Yuan-ti ziggurat to offer their sacrifices - exceptional members of their own tribe, chosen for beauty, strength, or cleverness, to be converted by the priest into a servant of the snakes. The huge, serpentine creature would summon the chosen with a single massive, clawed hand, beckoning them to the altar. On either side the misshapen mistakes - the broodguards - would slobber and gibber, clutching themselves, jeering, eyes malicious with jealous hate and anticipation.
On the altar, the chosen would accept a small, earthenware pot. Those who struggled were held down, the magical poison poured into their choking, gasping mouths; but many were proud to be selected and would hold the casque high, gulping at the viscous liquid greedily, eager to please their new masters. It was never until the next year, when the tribe returned, that they would know the fate of their friends, sons, daughters, lovers - whether their bodies, mutated by the Yuan-ti elixir, would twist into monstrous broodguards or solidify into one of the elite - the elegant, serpentine guards and spies of the serpent lords.
These latter would sometimes return to deliver messages, to demand tribute for the temple, or simply to see those they'd left behind; but no matter how missed, the chosen were always unsettling to their loved ones, made distant by the secret change in their blood. Their kiss, too, was poison - forbidden touch, they would linger, their slivered, serpentine pupils focused on their loved ones, before fading back into the jungle.
In her fourteenth rainy season, Nagaina joined the ranks of the chosen. Trembling, she took her place on the altar, accepted the rough clay bowl, lifted it to her full lips and drank.
In the days of excruciating pain that followed, Nagaina's body warped and twisted. When finished, she had ascended - she was a tainted one, a "hidden serpent." More than her companions, she took to the change; never a particularly athletic girl, she found her new ability to shift forms intoxicating. Under her masters' tutelage, she explored the more exotic of snake-kin - displacer serpents, shadow asps - creatures of sinister and unique power. Trained as an assassin, she became adept at stealing into human encampments, eluding detection, and leaving her victims locked in a poisoned death rictus - murdered in their beds, with no trace of their killer save for tiny fangmarks.
But what impressed the serpent lords most was the powers she unlocked from her deepest mind. Some trace of her people's draconic origins was strong in Nagaina, and perhaps that ancestral tie was what led her to unlock a deeper reserve of psionic strength than others among the chosen. Whatever the source, she had a unique ability: she could mimic not only the physical form of magical serpents, but tap into their supernatural powers as well. As she became more and more powerful, she began to experiment, learning how to best use her new abilities. She would slither through walls as an incorporeal shadow asp, elude attackers and allow for deadly strikes as a displacer serpent, and fly up unscalable cliffs as a sailsnake. She would change her form and milk her own poison, granting her arrows a deadly extra bite.
When she had grown enough, she escaped. Her masters gave little chase; though they valued her, they were unconcerned with her "vacation" - their most powerful servants almost always left the temple for a time.
Nagaina is not evil, per se; simply self-sufficient. She is elegant and beautiful, if somewhat unsettling; something about her, even in her human form, speaks of her serpent heritage.