I wondered if it had anything to do with the other executioners at first. I tried to see if there was a pattern in their defining character traits, but idk if that really led me anywhere. With his back turned to the grineer in the first image, it almost looks like he'd be with the other executioners instead of fighting them. The scene almost looks like they're getting ready for conquest. I also thought about how the images of the skin in white made the helmet look similar to a skull (Overwatch's Reaper, sry) and then I thought of the Finnish sniper Simo Hayha who was called the "White Death" could be thought of as an executioner. A broad net, but I hope I'm close -.-