Defense line up

How is this determined? I assumed it was just your 3 strongest players. But I fight people and their defense cards will change. Is there a way to change up your defense?

It’s the last team that you used to conclude a round in a particular event. So you have different defense teams between SHIELD simulator, Active Tourney, Lightnight Round, based on the last round you completed in those areas.

Makes sense! Very helpful. Thank you Sir!

Also, you make retaliations against the team that attacked you.