Bree's changes had progressed to where Lena's were when they'd started having sex. Lena now resembled a bipedal horse, from her hooves to her thick legs, to her sheath and tail to her muzzle. The only thing that remained human were her hands. But the nails were quickly blackening.
"Oh god.. why does this feel so damn good?" Lena thought as her lips pulled off Bree. There was a sucking noise that ended with a loud "pop" as Bree's cock was freed from Lena's cunt. Both girls' tails lashing about, fanning their musty pussy.
Lena licked her thick lips admiring her friend's half-furred body. Meanwhile, she was completely covered in fur, not a single patch of pink flesh left. Except on her throbbing cock. Though both had orgasmed, they were still both considerably hard. And they only got more aroused the longer they looked at each other's body.
"Lena... I... you look incredible." Bree complimented her friend, though the remaining rational part of her brain kept screaming that she did not look incredible. But the corruption from Bast's magic ran deep, drowning out the little sensibility either girl had left.
"I feel incredible." Lena said with some difficulty due to her new mouth. She stamped a hoof o the ground and look at Bree. Bree returned a submissive look, and proceeded to turn around.
"I want to be just like you. Please, I need you inside me." Bree said, reaching back to expose her gaping slit. The pink flesh inside was pulsing to the beat of Bree's heart, in and out of her mare pussy. Lena was drawn forward, and she put two slightly enlarged hands on Bree's hips. Her fingers had begun to fuse, and the black nails spread out. It wouldn't be long before Lena had hooves for hands.
"We.. shouldn't." That small voice inside Bree's head echoed. But when Lena bent over to kiss Bree's cheek, and rub her cock against Bree's outer lips, the small voice was eliminated. Bree moaned so loudly as the head of Lena's horsecock pressed against her clit.
"Oh, oh! Yesssss." Bree screamed as Lena inserted herself further and further. Bree couldn't believe how much of Lena's cock she could take. Every time she thought Lena would stop, more pushed inside. When Lena's balls finally hit Bree's lips, Bree could feel her friends cock buried deep inside her womb.
"Oh god yes! Fuck me! Fuck me Lena! Please, fuck me with all your might!" Bree begged. Lena smiled and slowly pulled back. Bree's lips clung to Lena's dick, sending shivers up Bree's spine. As her arousal built, her changes progressed.
Her ears tapered to points, held high on the sides of her head. Her already dark hair turned jet black, and the thick pelt of horse hair travelled up past her naval. As soon as Bree's entire body was covered in fur, her face started pushing forward. Her nostrils allowed for greater air consumption, so she took deep breaths to heighten her experience.
Behind her, Lena's arms had finished regressing into horse limbs. Her back cracked, and forced her to lean over Bree's back to continue her fucking. Her legs snapped to a downward stance, leaving Lena quadruped. Her hair pulled back to the top of her now lengthening neck. Soon she had a dark brown mane thrashing about. Her forelock was short, and a small white star had formed between her eyes.
Bree pushed her ass backwards, at the same time falling forward onto her own transforming hands. But she didn't even notice her changes. Bree's head was bent down so she could suck her own cock. Her breasts (furred with large black nipples) hung pendulous and full just like her testicles.
"Need more. Change me more!" Bree gasped as her body shuddered. She began licking the top of her head, eventually her tongue finding her slit. It was made easier now that she had a horse muzzle, and a big thick tongue.
"Yes! God, you feel so good Bree! It feels..." Lena cried out as her balls began to tighten in their furred sack. Bree could only whinny in agreement, her mind at a loss for words.
Bree slide down to her hands, now completely hooves, as her back and hips realigned and reshaped themselves to match a horse's. Lena's transformation completed at her teeth fell out and new molars replaced her meat eating teeth. Bree's changes soon caught up as her body was covered in black hairs, and her mane flourished.
"So close. Just a little more." Bree thought.
And then, it was over. Lena came, torrents after torrent of cum exploding into Bree's mare pussy. It absorbed as much of the spunk as it could before letting the rest overflow onto the floor. Bree's cock exploded in her mouth, and she drank every last drop.
Once the two calmed down some, and Lena pulled out of Bree, the two herm equines nuzzled each other. Bast laughed, and made herself visible to the two new steeds. They'd taken things a bit too far, since she had intended for them to just turn into horses from the waist down. But this was fine too.
"My new steeds." she said, her cat-like eyes gleaming at the two before her. Instinctively, the girls lowered their front halves toward the goddess into a sort of bow. They were now servants of the goddess. Living to service as both a mount, and a beast of pleasure.