It can be assumed that Blizzard will quickly fix the error.
You can only master seasonal content in Diablo 4 with new characters: at the start of each season, the hero must be created and upgraded again. It turned out that there is a way to drag an ordinary, already pumped hero into the seasonal content.
Players have found that Diablo 4 does not quite correctly handle a short client disconnect from the network. To get into seasonal content as a regular character, you need to do the following:
Enter the seasonal world in co-op mode. Disconnect from the Internet and wait for the message in the game that the connection is interrupted. Reconnect to the network. Enter the game as a regular character – he will be thrown into the old co-op session.
Once in the seasonal world, a regular hero can do everything the same as a seasonal one – for example, get legendary items with seasonal aspects. But items with unique seasonal mechanics will only work in the seasonal world.
In addition, through the seasonal world, you can transfer items from a regular character to a seasonal one. To do this, you need to use the fourth tab of the chest, common to both characters.
Blizzard is expected to close this bug as soon as possible. It is difficult to say whether the developers will punish the players who managed to use the bug.
This is interesting