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:
Artifact spells:
Cursed Totem
Null Rod
Black spells:
Dystopia
Stench of Evil
Extinction
Bereavement
Blue spells:
Hydroblast
Blue Elemental Blast
Chill
Douse
Green spells:
Tsunami
Hurricane
Oath of Druids
Red spells:
Pyroblast
Red Elemental Blast
Flashfire
Havoc
White spells:
Justice
Drought
Warmth