Storage Matrix

Oracle Text

As long as Storage Matrix is untapped, each player chooses artifact, creature, or land during their untap step. That player can untap only permanents of the chosen type this step.

Card Rulings

10/4/2004 This card’s ability does not override effects which prevent a permanent from untapping.
8/1/2005 Permanents with multiple types untap if any of their types is chosen. For example, an artifact creature untaps if either artifact or creature is chosen.
8/1/2005 If another effect limits the number of permanents that untap, that number combines with Storage Matrix’s effect. For example, Imi Statue says “players can’t untap more than one artifact during their untap steps.” If both Imi Statue and an untapped Storage Matrix are on the battlefield, and you choose “artifact,” only one artifact untaps.