Boss Rush (EEN-EN047) - Elemental Energy Unlimited

The controller of this card cannot Normal Summon or Set. During the End Phase of the turn that a monster on your side of the field that includes "B.E.S." in its card name, or is named "Big Core", is destroyed and sent to the Graveyard, you can Special Summon from your Deck 1 monster that includes "B.E.S." in its card name, or is named "Big Core".