WARNING: This game does NOT support Windows Mixed Reality Headsets with Original Controllers. It DOES have support for the HP Reverb G2 controllers. If you own the original headset and buy the game you will need to create your own Input Bindings for the controller. A guide can be found pinned in the Steam Community Discussions.
Link to pinned thread with a list of supported Headsets & Controllers.

Windows 10 is REQUIRED.

Uphold The Realm is a tower defense game that leverages VR to provide a uniquely immersive experience. Take all of your standard tower defense tropes and mix in the ability to experience it all in First-Person. Take command of your wargames style campaign map to interact with levels and manage towers. When your ready - Shrink down onto the table and use your archery skills to defend against the oncoming hordes. Inspired by Sanctum and KingdomRush.

Features

• Multiplayer - Up to 4 Players
  
• Build and Upgrade Towers - 4 Towers with 3 Upgrade Levels
  
• Full Modding Tools - Customize everything! (Monster Stats, Tower Stats, Levels, Waves)
  
• Use your Archery skills to defend your base
  
• Manage your towers from above and then Shrink down to attack the oncoming horde
  
• Over 20 different monsters - Land & Flying (10 out of 20 Implemented)
  
• Diverse Campaign Map - (7 available out of 13 for the first Campaign)
  
• Talent System - Customize your strategy
  
• Level Ranking System
  
• Multiple Difficulties
  
• Smooth Locomotion or Teleporting
  
• Leaderboards

Modding Tools

Link: Guide for game modding tools can be found here.