In the arena requirements there is a ban on the use of heroic dragons, but the opponent chooses with a heroic dragon!

@Евгений-Гайдук He May have been demoted from the war battles, which allow Heroics. If you lose enough trophy’s that can happen.

@LilCricketPa why again heroic dragon? even with the strengthening of the elements of metal if he does not have this element ????? This is a bug !!!!!!

Look at the amount of trophies, it is at 5200, which is the minimum requirement for Dark 1. You are on Metal 2. Usually bugs happen and SP usually fixes them.

@Евгений-Гайдук You are short before reaching the next stage. The opponent always has some more trophies than you have. So thats why. In the next stage heroics are allowed.