From an official press release from Konami

No matter what your strategy, the Circuit Break booster set is the next step forward. Three new monster themes are set to electrify your Duels: the Krawlers are an insectoid swarm that freeze your opponent’s monsters and leave them defenseless. The Altergeists are powerful techno-poltergeists, using the Graveyard to control the living. And Revolver’s “Rokket” monsters combine with Borreload Dragon to take aim at your opponent’s monsters with sharpshooting abilities. But that’s not all: Circuit Break is packed with legacy cards for fan-favorite Decks, plus new Spell and Trap cards you can play in any strategy.

Gouki Thunder Ogre and Trickstar Black Catbat power up Decks from Code of the Duelist, while legacy cards like Fire King Avatar Arvata, Mermail Abyssnerei, and Mecha Phantom Beast Raiten power up popular themes like never before! Incredible new Link Monsters like Borreload Dragon and Akashic Magician bring deadly effects to almost any strategy, while Destrudo the Lost Dragon’s Frisson makes Synchro Summoning easier than ever before, and the stunning Trap Card Evenly Matched turns the tables entirely, wiping the field just when your opponent thinks they’ve triumphed.