Torchlight: Infinite is known as a season-based game. When the season ends, characters and items obtained during the season will be merged into a permanent server. Your Primocryst, however, together with most items purchased using Primocryst, including Pactspirits, Outfits, Monthly Pass, Inventory Slots, and Stash Pages will remain valid for characters in both the permanent server and the seasonal server.
All your unlocked heroes, hero traits, Pactspirits, and appearances will carry over to the next season. They count as the shared assets of your account, so they can be used by all characters you create in the same account. However, this only applies when they are on the same server. For example, all characters created on the US server can only use assets of the account that are on the US server.
Other things like Season Passes and Auction Booth Tabs will expire at the end of the season and will need to be repurchased in the new season.
The characters of the Dark Surge season will be transferred to the permanent server after the new season starts. Hunters will need to create a new character to participate in the challenges of the new season.
After the new season starts, Hunters can enter the new season server and develop their characters from scratch. In the new season, you can experience new gameplay and get season-exclusive items by challenging the new season Boss.