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I was trying to cast Fanning the Flames with its buyback option, and I couldn't for the life of me figure out how to do it. How does one use a card with buyback?

Buyback is added to the cost and can be selected on action window (see the attached picture). I will try to add a label to a more easy way to use.

ARe you sure you did it the right way around? I would guess that the option where you pay 6 mana and get 1 damage would be X=1, buyback 3.

Ummm, I was recently wake up and I must be sleeping a bit when i did the image. Youa re rigth. Labels are ordered in wrong way, but the image shows both kind of the spell