Story premise: A human princess (20-26, redhead, petite) smuggles away the last goblin after the rest of them have all been killed by the soldiers throughout the empire, out of pity and misplaced pacifism. She hides it in her personal quarters, the only place that won't be searched.
The goblin plays nice and starts to cook and make tea for her, putting his cum into the meals to slowly turn her into a broodmother for the next generation of goblins. The change happens slowly across a few weeks, with her curves becoming more thick and her demeanor becoming more crude and horny. Three weeks in, the last change starts to happen which is her losing attraction for all humans and starting to lust after goblins particularly. At this point, her tits and ass are massive and she starts sucking him off directly which accelerates her transformation and cements her allegiance to her new cause and identity. With that, he impregnates her and her belly starts to swell.
Bonus / extra story content: She starts kidnapping her maids and young noblewomen friends, starts converting them as well.