The Mirror Mode is often seen as one of the most skilled: same deck, same starting hand, what makes the differences are your decisions and the use of the Mirror card.
Even if this skill comes with time and practice, here are three tips to help you overcome the Challenge:
Don't rush into battle and use the few seconds at the start of the game to analyse your deck. It's the same for your opponent!
What are the synergies? What card will be difficult to deal with? Take the time to think about the strengths and weaknesses of the deck.
After analysing your deck, identify what the win condition is. A win condition is a card designed to inflict severe damage to the towers. You can have one or several.
It's the cornerstone of your deck and will probably be the key to your victory.
Now that you have a good understanding of how your deck works and what you should do with it, think about the counters... or the lack of them.
Do you have air units but no anti-air? Swarm units but no splash damage or small spell? The fewer counters a card has in the deck, the more powerful it will be in the game. If it's good for you, it's also the case for your opponent!
Don't forget the basics for every battle in the Arena: manage your elixir wisely and keep track of your opponent's card cycle! With all those tips in mind, the Mirror Challenge will be a piece of cake.
See you in the Arena!