Crew is a new mechanic debuting in the Rekindled Rebirth set.

It is related to the ship item type and the pirate ally's alignment, but not only.
Allies can "join the crew" of a Ship (displaying similar to an attachment), allowing for various effects to take place involving allies in the Ship's crew.

Only Allies can join the crew; therefore, artifacts that become allies are unable to join.

SOME ARTIFACTS THAT BECOME ALLIES