Defense position monsters will get banished, preventing them from activating their effects that usually happen if they get sent to the graveyard.
Monsters have to be in DEF position to resolve this effect.
It can only work if the attacking monster still go through with the attack.
Using Windstorm of Etaqua will not work with this card since the attacking monster will get switched to defense. You can use cards like Sphere Kuriboh to target specific monsters, but usually Tragedy is a better option.
So Dkayed made a "Ahead-of-the-Meta" move when he introduced Flip Flop Frog into invoker decks because it counters Cocytus. Well this card is more efficient and not at all situational. This is because people have a habit off putting all the other monsters except for the attacking monster into defense position in fear of the Wall of Disruption or Drowning.
i used this card once and coincidentally matched up with amazoness ..and amazoness princess attack with its effect activated and summon queen on the field in defense ...banished queen and enemy rage quit ..LMAO
Not really: you're not allowed to activate Dark Mirror Force if your opponent has no defense position monsters, so you can't do "I activate Dark Mirror Force and chain Etaqua". You're far better off with Tragedy.