Jet, Freedom Fighter

Whenever you cast a historic spell, create a 1/1
green Rebel creature token.
(Artifacts, legendaries, and Sagas are historic.)
Jet gets +1/+1 for each Rebel you control.
Whenever Jet attacks, you may pay {4}. If you do,
creatures you control get +X/+X until end of
turn, where X is the number of historic
permanents you control.