This DLC provides no in-game content or additions. Everything in the game is available to everyone for free, forever.

The DLC is intended as a way to show your support for the developers.
It'll allow us to keep making games, and keep releasing them for free and unpaywalled.

That being said, this DLC does include out of game content:

• Skill Tree Wallpaper 4k
  
• Dalmati Wallpaper 1k
  
• Them Showcase Base Wallpaper 1k, both Caged and Uncaged

Also, feel free to indulge in one unit of more rarefied self-satisfaction for having supported an indie dev.