BaseLib is a Slay the Spire 2 mod intended as a base for other mods to use as a dependency.
As dependency: <PackageReference Include="Alchyr.Sts2.BaseLib" Version="*" />
You will need to download the .dll and .pck from releases and put them in Slay the Spire 2/mods.
Placeholder:
If using locally, adjust filepaths at top of csproj. Use resulting .dll as a dependency for your own mod.
Temporary quick mod start guide: https://github.com/Alchyr/ModTemplate-StS2/blob/master/README.md