You may cast Hazel's Nocturne with no targets just to have each opponent lose 2 life and you gain 2 life. However, if you do choose any targets, and all those targets are illegal as Hazel's Nocturne tries to resolve, it won't resolve and none of its effects will happen. No player will lose or gain life.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.