Magic: the Gathering - Datenbank

At the beginning of your upkeep, for each land target player controls in excess of the number you control, choose a land he or she controls, then the chosen permanents phase out. Repeat this process for artifacts and creatures. [i](While they're phased out, they're treated as though they don't exist. They phase in before that player untaps during his or her next untap step.)[/i]