Asking Non-Jew To Do Melacha D'Oraita

You may not ask a non-Jew to turn ON a light or turn ON heat, or other d'oraita violations of Shabbat--even for a mitzva or for oneg Shabbat. However, you may ask a non-Jew to do a melacha d'oraita for any of a sick person's needs, even if there is no danger to the person's life.
Note You may tell a non-Jew to do melacha, even if it is d'oraita, for a mitzva or oneg Shabbat only if it is bein ha'shmashot (between sunset and dark).