The season is a battle pass. The paid tier is all cosmetic, but the prices on the shop are so ridiculous. This game should have been free to play. But Blizzard is so greedy now, even with WoW Classic fueling their traditional subscription cash cow more than it has been for a while. It’s sad to see the decline of this once-awesome company.
I bought D4 recently when it went on sale, and it is pretty fun, but I would not recommend paying full price.