I started the arena campaign and chose a legendary card. I took cards, observing the conditions of the legendary card, so that there were no duplicates of cards. In one of the last choices, I was given a choice of 3 cards that I already have in the deck. And my legendary card becomes useless. I sacrificed the value of the cards to fulfill the condition, but the game itself told me that I cannot fully reveal the positive side of this legendary card and I will suffer because of the lost benefit, when choosing previous cards. Thank you for an interesting experience in the game!!!
it always happen, but after the first lose you can change your duplicated cards