Fionna saw multiple possibilities with her form that made her aroused, she decided to change her body with the multiple monster DNA inside her.
First she returned to her naked human form without any monster qualities, then she used the Oni and Amazonian DNA to make herself strong and immense, being almost 30 feet tall, then she grew 7 extra pair of arms on each side of her torso, having a total of 16 arms as the same time two pairs of breast appeared in her chest, the second one replaced her nipples with functioning mouths that could absorb monster DNA and the third pair replaced her nipples with vaginas that could also absorb DNA, her lower body replaced her legs with a large amount of tentacles attached around her hips, many tentacles were replaced with snake tails, giant cocks and kitsune tails, all of that lower extremities had a hole were they could shoot spider web, also she had 4 pussies below all the multiple extremities. Her back grew four succubus bat wings while her neck turned into a giant hydra snake neck, she grew two extra hydra necks with heads, one on each side of her original one, the left head had arachne attributes (8 eyes and fangs), while the right head had snake attributes (yellow vertical eyes and long tongue), the head on the center was her normal human head but with vines instead of hair.
Fionna appreciated her monstrous but marvelous body while masturbated her pussy nipples with her multiple arms, at this point no other monster girl could defeat her since if her neck get chopped she could easily re attach it with her dullahan abilities and defent herself with her scythes, now she could do anything she wanted and absorb more monster girls to have every monster girl DNA inside her and become the goddess of this world.