TacticianG 20

You have to win a single duel using a deck made in the deck builder, not using the deck wizard.

If you don't know how to build a deck, like I don't, here's the easy way. You can turn any deck that you made using Deck Wizard into a custom deck!

Simply:
Go into your decks and click A to edit the deck you want to use to get the win. Then, click convert and confirm your choice.
Now, you should be editing the deck. Just press B. It should now say 'CUSTOM DECK' underneath the deck's name.


Now, win with this deck and the achievement is yours