Unnatural Selection
1:choose creature type other than wall.  Target
creature becomes that type untill end of turn.
If an opponent plays a spell or ability that can target a Flagbearer in
play, the opponent chooses at least one flagbearer.
With a flagbearer in play, use Unnatural Selection to switch its type to
another type (anything other than flagbearer).  This makes the
flagbearer an illegal target and the opponent must still target a
flagbearer.  We know the famous equation:
                Spell + illegal target = discard with no effect
Tell me if this works!