702.39. Storm (From the Comprehensive Rules)
702.39a Storm is a triggered ability that functions while the spell is on the stack. “Storm” means “When you play this spell, put a copy of it onto the stack for each other spell that was cast before it this turn. If the spell has any targets, you may choose new targets for any number of the copies.”
702.39b If a spell has multiple instances of storm, each triggers separately.
The EPIC Storm (TES) is a deck with win conditions that use the storm mechanic. Over time these win conditions have changed, in the past the primary win condition has always been Tendrils of Agony - but not anymore! In current lists of TES, Empty the Warrens has become much more of a focal point. Its one of the differentiating factors between TES and its cousin Ad Nauseam Tendrils. TES can be defined by its Goblin tokens from Empty the Warrens as well as its other red cards - Rite of Flame and Burning Wish!
A few key strengths to TES that separate it from the other storm combo decks in Legacy are its blazing fast speed (while staying consistent and often backed by protection) which allows the deck to win before the opponent can cast their hate spells, high tutor density, the utilization and flexibility of Burning Wish, the strength of its ability to win off of the card Ad Nauseam, and its ability to reliably play multiple colors in a consistent manner.
Since then The EPIC Storm’s incarnation it's gone from a niche deck to a powerhouse played all around the world, with some impressive finishes!