B.E.S.

B.E.S. is a series of Monster Cards usually identified by having B.E.S. in their card name, but also include Big Core and Big Core Mk-II. B.E.S. stands for Bacterium Empire Ship. The B.E.S. cards are based off of the Konami video game Gradius.

B.E.S. cards effects include putting counters on them when they are summoned and cannot be destroyed by Battle. After battling a monster, a counter is usually removed at the end of the Damage Step and if they battle without a counter they are destroyed at the end of the Damage Step. The counters represent the "shields" on most bosses that represent their much higher ability to take damage than normal enemies. Of the B.E.S. monsters, only B.E.S. Covered Core has a chance of not losing part of its shield - representing the enemy attack only striking an invincible part of the exceptionally well-armored boss rather than the vulnerable location.

Although these cards can work well in a variety of decks, they are usually seen in a Boss Rush Deck