Mai Valentine's deck changes. I just had a duel where she had 3 AMAZONESS VILLAGES!
I seriously cannot beat her and I am having a very hard time beating Mai Valentine. Like an extremely hard time. I do not have the cards for those decks for I am a new duelist and I started three weeks ago. I rarely win and I am trying to get the two SR Harpie cards, but it seems I have gotten every card EXCEPT, the Harpie cards. I need some serious help.
Do you have Paradox Brother unlocked? if so, try use labyrinth builder skill.
I have found that this can be good for farming the LDs, but especially Mai, because she is mostly about attack increase and swarming you. But once you get too much more attack points then her, there is not much she can do about it.