Players can lose more life than they have. For example, say you're playing a multiplayer game in which one of your opponents has 3 life and your other opponent has 10 life. If you cast Exsanguinate with X of 4, your opponents will wind up at -1 life and 6 life, respectively. You'll gain 8 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.