Cavalry Master | Magic: The Gathering
Formats Cavalry Master is Legal in
Official Oracle Text for Cavalry Master
Other creatures you control with flanking have flanking. (Each instance of flanking triggers separately.)
Official Rulings for Cavalry Master
9/25/2006 : If a creature without flanking is given flanking by another effect, then this ability will grant a second instance. Similarly, if a creature loses flanking, then it won't get the Calvary Master instance either.