"The Fracked" are the unfortunate souls brutally consumed and subsequently controlled by the crystal.
The enemies found in the game weren't always zombie-esque creatures. They evolved as the aesthetic, narrative and gameplay requirements changed through production. Initially, we wanted our "bad guys" to conform to the highly trained mercenaries of the early versions of the storyline, but it was clear from a fairly early stage that depicting special forces soldiers brought with it an expectation of advanced AI behaviours and a large amount of animation requirements because of that. In a similar way to how we found our artstyle, we played to the strengths of the PSVR hardware and found ways of easing the burden on the processing.
As the storyline coalesced, it allowed us to be more creative with the look of the enemy characters and move toward creatures controlled by disease or some alien influence. This helped simplify the animation requirement and also change the behavioural expectation of the player. This was a win-win for us as we had much more fun with the new enemy designs that were also nowhere near as costly to the framerate, allowing us to spend processing power elsewhere.
We tried out some pretty out there crystalline creature designs but eventually dialled that back to the hybridised humans that were unlucky enough to be in or working near the mines at the time of the inciting incident. We emphasised how the massive crystalline shards and lumps deformed their bodies and created striking silhouettes that also served to visually distinguish them on the battlefield and contrast against the already colourful background. This conforms to our art directional goal of clarity and readability in VR.