Rule 611.2b

Some continuous effects generated by the resolution of a spell or ability have durations worded “for as long as . . . .” If the “for as long as” duration never starts, or it ends before the moment the effect would first be applied, the effect does nothing. It doesn’t start and immediately stop again, and it doesn’t last forever. Example: Master Thief has the ability “When Master Thief enters the battlefield, gain control of target artifact for as long as you control Master Thief.” If you lose control of Master Thief before the ability resolves, it does nothing, because its duration—as long as you control Master Thief—was over before the effect began.

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