Xenic Poltergeist

{T}: Until your next upkeep, target noncreature artifact becomes an artifact creature with power and toughness each equal to its mana value.

Masters Edition IV

{T}: Until your next upkeep, target noncreature artifact becomes an artifact creature with power and toughness each equal to its converted mana cost.

Fifth Edition

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T: Until your next upkeep, target noncreature artifact is an artifact creature with power and toughness each equal to its total casting cost. (That artifact retains all of its original abilities.)

Renaissance

Rinascimento

Fourth Edition

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T: Target non-creature artifact becomes an artifact creature with power and toughness each equal to its casting cost. Target retains all original abilities. This change lasts until your next upkeep.

Wears off at the beginning of the upkeep, not during upkeep.

A noncreature permanent that turns into a creature can attack, and its {T} abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn't matter how long the permanent has been a creature.