(Anthro)(Cumflation)(Growth) Whilst trying out a futa spell With Celestia Twilight discovers that Celestia knows a spell to convert cum to size and mass with heavy emphasis on curves. this causes Twilight to try and cum bigger and bigger then the last time causing Celestia to slowly become more and more buxom… And then taller and taller as well.

“ - Oh,” Celestia choked out. “Oh, my dear Twilight. I feel so full.”

Twilight just moaned as Celestia rode her dick. The larger princess’ voluptuous body squished against her groin with each thrust. Celestia’s big, globular ass almost seemed to expand each time it flattened against Twilight’s crotch, the smaller princess just following along for the ride as her stallionhood throbbed and bulged inside of Celestia. Soon, it throbbed harder than ever, bulging until it could bulge no more -

And then her balls were swelling, churning, emptying their load inside of Celestia’s marehood. Twilight cried out, her back arching on the bed, her hips thrusting up as far as they could until she bottomed out inside of her mentor’s cunt. Celestia just moaned as Twilight pumped a good half-gallon of cum inside of her. She squeezed her breasts and rocked back and forth, her thighs milking Twilight’s cock for all that she was worth.

Then Twilight’s orgasm slowly tapered off. Her cock throbbed once - twice more - and then finished with a final, thick rope of cum that splattered against Celestia’s insides. The larger princess just licked her lips, leaned over, and - with Twilight’s cock still inside her - took Twilight’s lips in her own and gave her a long, hot kiss.

Soon, though, the weight on Twilight’s hips began to increase. She met Celestia’s kiss hungrily, their tongues dueling as her erection began to throb once more. One big orgasm wasn’t enough, it seemed - neither for her nor Celestia.

Celestia pulled away, a line of saliva running from her muzzle to Twilight’s. Twilight smiled weakly up at her - and then blinked. “Tia,” she murmured. “You look…bigger.”

“Do I?” Celestia said innocently. A wicked smile crept onto her face. “Looks like that spell is working after all.” She squeezed her breasts together, and Twilight watched with complete fascination as they swelled at her touch. Soon, Celestia’s supple titflesh was spilling through her fingers. Celestia herself had taken her enlarged, coin-sized nipples in her hands and was rubbing them, moaning softly.

Twilight moaned herself as Celestia’s ass became heavier and heaver on her hips. Her mentor’s bountiful butt jiggled gleefully as it spilled over Twilight’s legs. Soon, Twilight was gasping as her mentor’s thick, padded pussy squeezed her cock over and over again - and in no time at all, she was cumming again, her hips jerking rapidly as she spewed double the amount of spooge into Celestia’s marehood.

Celestia just groaned. “Oh, yes, Twilight. Very good.” The growth began again in earnest, her breasts swelling until each one was larger than Twilight’s head, her ass rounding out even further as her thighs thickened with padding. It soon became obvious that she was growing in other ways as well - Twilight watched through half-lidded eyes as her mentor’s head inched up above her, stretching toward the ceiling, until it was at least a foot higher than it had been when they had started. For another dozen seconds, Twilight felt her cock seizing and throbbing, filling Celestia up with more and more cum and Celestia converting that cum into size just as quickly.

And then, finally, Twilight’s second orgasm was over. Carefully, Celestia removed herself from Twilight’s cock and laid herself down over Twilight, her student giving an “oof” as her teacher’s weight pressed down on her.

Celestia’s enormous breasts pushed against Twilight’s own, much smaller bust. Her massive thighs - almost half as long as Twilight’s entire body now - rubbed and squeezed against Twilight’s feet and lower legs, as Celestia ground her pussy against her. Just barely, Twilight could make out the rounded top of Celestia’s globular ass jiggling proudly in the air above her.

Celestia just smiled and shifted her weight, a task made all the more impressive by what must have been an eight-foot-plus frame. Twilight suddenly felt so small - and yet, if the throbbing in her cock was anything to go by, she’d never been bigger in all of her life.

Celestia just kept smiling and, tenderly, ran a hand through Twilight’s hair. “What do you say?” she murmured. “Shall we see how big I can get?”

Twilight had no problem with that.