(This takes place in a medieval-like setting)

You're a deer boy, short, fluffy, not so strong and pretty much prey for most other anthros, but even then you geared up and became a paladin, you could heal really well, like above all other paladins in healing, but under in damage, you got into a duo with a poison dragon named Sini, black scales with purple underscales and deer-like ears, purple inside, tail and back spikes and curved horns, he's wearing purple-glass round glasses with a golden frame and no legs, a light borwn leather poncho-like vest and dark brown shorts, he's pretty strong too, strong magic spells, but only to attack and defend, so you being a healer is a huge deal, plus, he didn't see you as a prey anthro, but as a friend, and he was a big guy, pred too, so your enemies ended up making him have a dad bod and you become a good team, but one common day like the other, you talk about clearing and dungeon and getting a dark magic artifact, but two dragonesses get in your way, one a deer dragoness hybrid who's a druid, brown fur with green tips and a eastern dragoness with panta-black scales, grey underbelly, three plate-like scales on her muzzle, also having deer ears and antler-like horns, you try to be friendly and wave hello, but they seem really mad, and a glint of greediness is percieved in their eyes, Sini tries to de-escalate but they're set on in defeating and swallowing you both so you don't go said dungeon and claim the treasures all by themselves, Sini having none of it, goes to them, grab them and swallow them instead, before gulping you could see their muzzles sticking out, backtracking and willing to accept the split of the goods made by Sini, but no, down the hatch they go, Sini chuckles and lets his gut make a speedy digestion and lets out a loud rumbly belch, his belly burbles in a rather concerning way as it absorbs the now-slop former dragonesses, two new heads start growing from the sides of his neck, membrane covering them as it naturally dissolves, their necks grow to 2 feet long, the body grows to 11 feet tall, the tail thickens and grows longer and goes from male to an incredibly curvy female one, it was the dragonesses! Their heads, now in a hydra setting, keeping their former characteristics, now sharing the same color palette of Sini's body, which is now fluffy with what it seems to be deer-like fur, you watched the whole thing go down, and you're feeling conflicted, worried for Sini, shocked and a little bit scared by this hydra version of them, since by the looks of it the new heads kept all memories and personalities, but also, turned on, they were attractive not going to lie, and a hydra too? That somehow sounds appealing too, but careful, it's still all new.