Target creature and all other creatures with the same name as that creature get -3/-3 until end of turn.
2/1/2014 Bile Blight has only one target. Other creatures with that name are not targeted. For example, a creature with hexproof will still get -3/-3 if it has the same name as the target creature.
2/1/2014 If the target creature is an illegal target as Bile Blight tries to resolve, it will be countered and none of its effects will happen. No creature will get -3/-3.
2/1/2014 The name of a creature token is the same as its creature types, unless the token is a copy of another creature or the effect that created the token specifically gives it a different name. For example, a 1/1 Cat Soldier creature token is named “Cat Soldier.”