I don't know if this information is already public but here are a couple of quick inferences I made by looking a the files. I'm not overly familiar with Valve's intellectual properties so I don't recognize any specific characters or franchises.
There's likely a hero named Yamato who has the abilities:
Shadow Form
Power Stance
Infinity Slash
Healing Slash
Flying Strike
There's a lot more hero information but that's the top one in the depots.
The game might be called "Citadel", or it may have just been called that internally at Valve.
The reason I suspect that is because of there appears to be a game folder called "citadel" which appears to be the main game folder.