A quick sketch of a priestess being corrupted into a serpent. Mature.
Sister Juliel knelt in front of the shrine of Al-Esh and tucked her white habit beneath her knees before bowing her head and beginning the night-time prayers. At the hour of Vigils, each of the seven shrines that ringed the convent had to be given prayer and their candles lit. It was a lonely, sleepy task, but a peaceful one.
A warm breeze crossed through the open windows of the shrine. Juliel paused, her lips sliding shut as she lifted her eyes and glanced out the window. Nothing stood outside but the shadow of the trees in the orchard. For a moment, she studied the dark, expecting to see the eyes of some owl or cat glinting at her, but there was nothing. Head bowed, she completed her prayer, then lit a thin taper from her lantern and held its tip, one by one, to each of the seven candles.
As she was about to light the final candle, a sudden wind blew so fiercely Juliel thought she had been struck. Tumbling to the side, she landed against the wall of the shrine, suddenly plunged into darkness. The candles and her lantern both had gone out.
Juliel crouched where she had landed for a few moments, wide-eyed and listening. There was not even the rustle of wind in the leaves from outside. Quietly, she traced the sign of the seven-pointed star on her chest, and began to whisper, "Blessed Al-Esh, please guide and protect my spirit..."
Again, the wind whipped across her, but this time, it seemed to curl around her, throwing her onto her back on the floor. The words were knocked from her tongue. Instead, she gasped for air, turning her head, peering into the darkness, and struggling to raise her arms. They were held fast to the ground, and she could almost feel a pair of unseen hands holding them there.
"L-let go of me, in the name of the Seven—aah!" she gasped. Her shoulders recoiled and her fingers clenched as a searing heat blazed against her wrists. A cracking, crinkling sound came to her ears, like the sound of parchment burning, as the sleeves of her habit began to constrict around her arms.
There was little light to see by, but Juliel's eyes were adjusting to the darkness. As she stared at her arms, she could see the white linen sink down against her arms, then split and crack apart. The sleeves of her habit were merging with her skin, becoming pale white scales that climbed her arms. Where the scales went, so too did the burning feeling, as if her arms had been plunged into searing hot water.
Her heart pounded against her ribs; her blood ran hot in her veins. "Stop! Help!" she cried, shutting her eyes and twisting back her head. She began to call out the names of the Seven, but was cut short by the linen tightening around her chest, squeezing the breath from her lungs.
Juliel fought to breathe. The spreading white scales across her midsection wrapped around her tighter than a shawl. They seemed to move and writhe of their own accord: pulling tight around her waist, drawing outward across her breast. That was not the worst of it, though. The worst were the fires inside her head, the pounding heat of the blood in her temples, and the fear that if her arms were not held down, she would not be able to keep herself from sin.
Whatever force was doing this seemed to sense her own fear. The grip on her arms lessened, then vanished. She gathered her hands to her chest, clutching them together, trying not to think about their smooth scales and curled claws. In the space between her gasping breaths, Juliel prayed desperately.
The unseen hands that had gripped her arms now seemed to take up her legs, drawing them off the ground, clutching her beneath her knees. Something was stirring within Juliel, something that lashed and twisted. It pressed its way from the small of her back, writhing out against the ground, sliding out into the space between her legs: a tail.
It was then that her skirt bore down around her, wrapping up her legs and growing tail both. The more she squirmed and fought, the more her legs sunk into the thick, muscular mass of her tail. The invisible hands pushed, kneading her knees and thighs down, while she fought, straining against the scales that gripped her tighter than her own skin. Foot upon foot of thrashing tail unfurled from her body, knocking over the shrine candles and dragging the tapestries from the walls.
All that remained to suggest that Juliel once had legs were the hips below her waist, which merged smoothly into the thick shape of her tail. And between them, nestled between her torso and her tail were—oh, Al-Esh forgive her!—a scaled mound, parted folds, a hint of pink flesh, and an unbearable ache.
"Nnh-no. This is..." she gasped. Her hands were balled into fists, clasped tight beneath her chin, but every undulation of her serpentine tail brought forth a fresh urge to reach down and sate that ache.
The unseen hands clutched the sides of her face now, pressing her head down against the ground. Her tail lashed against the floor and she cried out loud as the heat sunk into her already-burning cheeks. The wimple, draped over her head and across her shoulders, cracked and crinkled as it split into scales. A cobra's hood stretched out from either side of her neck, rising from her shoulders up to where both sides met atop her head.
Juliel's eyes rolled in her head as her mouth fell open. The scales climbing up her cheeks stretched and shaped her head, molding it like clay. A broad, tapered snout, with a pair of long fangs resting hidden inside her mouth. A white membrane slid over her eyes as the heat inside of her erupted, overflowing her body and sending her slumped to the floor. Her eyes rolled back open, now pale red. Her tongue slipped from her mouth, flickering in the air before sliding back.
"This feels..." she muttered, as her claws roved down her sinuous, scaled body, "So...sssinful." Her tail and spine writhed slowly as she mouthed the words of a prayer, uneven and hesitant, as if they were foreign to her now. She began to make the sign of the Seven, but her hand faltered and stopped.
She was no priestess any more. But had she ever been? The hunger burning in her heart, growing now with every minute—it was a lust she knew well. Perhaps this was what she had always been. It all came so easily now, from the desire driving her forward to the slithering sway of her serpentine body.
Juliel paused as she slipped through the doorway of the shrine, gazing up at the shadow of the convent and slowly flicking her tongue into the air. Years and years of denied welled up within her. She hastened herself and slid on silently toward the dormitory.