Enchantment - Aura, W (1) Enchant creature you control Enchanted creature is a Flagbearer. Whenever a spell or ability an opponent controls is put onto the stack, if that spell or ability could target a Flagbearer in play but doesn't, that opponent changes one of its targets to a Flagbearer.1
Illus. Darrell Riche
If this card is ever on a creature you don't control, it is put into the graveyard as a State-Based Effect. [D'Angelo 2001/06/15]
The requirement to choose a Flagbearer as a target only affects the choice of targets. It does not affect the check made for legal targets when a spell or ability resolves. So having a Flagbearer enter play after targets are chosen will not cause a spell to be countered. [Barclay 2001/07/09]