It only works once. If someone casts another spell after it triggers, but before that trigger resolves, then it will trigger again. The first time one of these triggers resolves, it will be sacrificed for the full effect. Any additional triggers on the stack will do nothing when they resolve because you will be unable to sacrifice it additional times.
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.
