What exactly are the Hearthstone Legends season rewards, please?

At the end of the month settlement is based on the highest achievement of the month, starting with a new card back at all levels above 20.

In addition, level 20-16 has a gold common;

15-11 has a gold rare and a gold common;

10-6 has a gold rare and two gold commons;

5-1 has a gold epic and two gold commons;

Legends have a gold epic and three gold commons. (In addition more Arcane Dust is given for higher levels in each bonus stage)