Hey there,

Valheim is currently in Early Access, meaning that it's not finished yet and will get more updates over time until it reaches a full release version ("1.0"). The devs have said that they don't plan on doing any paid DLCs.

You might want to give the pinned FAQ thread a read before buying:
https://steamcommunity.com/app/892970/discussions/0/3383905288030494726/

Have a good day!