Used in CCG Magic: The Gathering
. Used in major tournaments. It is a separate 15 card pile, aside from the main deck itself. It is composed of any cards that the player chooses but must be declared at the declaration of deck contents.
This is mostly composed of cards that either hose a specific color or a specific deck. Furthermore, in between matches, players are allowed to switch cards from their main deck with the sideboard on a one for one basis. They cannot drift off from this number and their main deck must be the same number as they started with before they switched cards with the sideboard.
Some popular sideboard cards are:
Stench of Evil
Blue Elemental Blast
Oath of Druids
Red Elemental Blast