Ellie is a witch with fairly minor powers, whose mistreated and humiliated by her mistress, because she is weird and flat-chested. Her mistress makes Ellie watch as she titty-fucks and has sex with a guy.
But the shame and humiliation gives Ellie the strength to cast a spell on her mistress that make her mistress start lactating. Ellie sucks on her mistress's tits, and starts draining her lips, tits and ass. Ellies breasts, lips and ass grow as her mistress shrinks.
Once Ellie has finally taken everything from her mistress, she forces her to watch while she fucks, titty-fucks and sucks off a guy.