The Vanguard supplements consist of oversized cards that modify the game. A Vanguard card is selected before the game begins, adjusting a player's starting and maximum hand size and starting life total. Any abilities printed on a Vanguard card are played exactly like those of an in-play Magic card; however, these abilities have no color, and damage from them isn't damage from a permanent of any type or a source of any color. A Vanguard card isn't a Magic card, so it can't be affected by spells or abilities.
These cards were used in several Arena seasons (starting in 1997), and were later available as part of a gift box.