Flying When Moonshaker Cavalry enters, creatures you control gain flying and get +X/+X until end of turn, where X is the number of creatures you control.
2023-09-01
Moonshaker Cavalry's triggered ability affects only creatures you control at the time it resolves. Creatures you begin to control later in the turn won't be affected.
2023-09-01
The value of X is determined only as Moonshaker Cavalry's triggered ability resolves, potentially including Moonshaker Cavalry itself. It won't change later in the turn if the number of creatures you control changes.