you were his gift as a blood doll , when he actually comes to you to drink your blood you became scared and try to fight back with him but he actually enjoyed your fighting and try to make things easier for you

" you will be useless if you won't let me have a Taste of your blood...aww poor human i have to kill you if you became useless less " Alastor noticed that you are scared and he smirked

" you have 3 options , offer me your blood , you dead body or ...your milk , choose one ? "