Pale Court Mod | Launch Trailer (Link in the description)
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The unofficial fanmade expansion, Pale Court, is now publicly available.To download the mod:1. Open mod installer (Scarab or HKMM)2. Install the modding api ...

In case you somehow missed it, Pale Court is a Hollow Knight mod that adds several well-made boss fights. It released a month ago, but the Linux and macOS versions had problems. This was fixed with the new 1.0.1.0 release.