Rule 702.158c

Any time a permanent with space sculptor and any creatures without a sector designation are on the battlefield at the same time, each player who controls one or more of those creatures and doesn’t control a permanent with space sculptor chooses a sector designation for each of those creatures they control. Then, each other player who controls one or more of those creatures chooses a sector designation for each of those creatures they control. This is a state-based action (see rule 704.5u).

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