Cascade

702.82. Cascade
702.82a Cascade is a triggered ability that functions only while the spell with cascade is on the stack. “Cascade” means “When you cast this spell, exile cards from the top of your library until you exile a nonland card whose converted mana cost is less than this spell’s converted mana cost. You may cast that card without paying its mana cost. Then put all cards exiled from the game this way that weren’t cast on the bottom of your library in a random order.”
702.82b If a spell has multiple instances of cascade, each triggers separately.