Historical Rules · 1 October 2009
Rule 800.5
Official source text from the 1 October 2009 Rules release
In a multiplayer game, the first time a player takes a mulligan, he or she draws a new hand of seven cards rather than six cards. Subsequent hands decrease by one card as normal. The Two-Headed Giant variant employs more extensive changes to the mulligan rule; see rule 806.6a.