Teferi, Timeless Voyager

Any continuous effects with a “for as long as” duration such as that of Awakener Druid ignore phased-out objects. Any such effects will expire if their conditions are no longer met after ignoring the phased-out objects.

Choices made for permanents as they entered the battlefield are remembered when they phase in.

Normally, phased-out permanents phase in during their controller's untap step. Teferi's last ability causes the phased-out permanents to not phase in until the duration has expired; they'll phase in during their controller's next untap step after your next turn.

An attacking creature that phases out is removed from combat.

Any creatures that phase in during their controller's untap step will be able to attack and pay a cost of {T} during that turn.

In a multiplayer game, if you leave the game after Teferi's last ability resolves but before your next turn ends, its effect lasts until your next turn would have begun. It neither expires immediately nor lasts indefinitely.