MTG Keyword Rules — Comprehensive Rules Glossary

One card (Space Beleren) has the space sculptor ability. This keyword ability causes creatures to gain sector designations.

A sector designation is a designation a permanent can have. The sector designations are alpha sector, beta sector, and gamma sector. Only permanents can have a sector designation. Once a permanent gets a sector designation, it keeps it until no player controls a permanent with space sculptor or an ability whose source has space sculptor. A sector designation is not part of the permanent’s copiable values.

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).

Some abilities include an instruction to choose a sector along with an instruction to perform an action on each creature in that sector. To do this, choose one of the three sector designations, then perform that action on each creature with that sector designation.

Two permanents are in the same sector if each has the same sector designation.