The following is set of from notes found in a derelict bunker.

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[12/29/2160]
The figures we've seen in the distance for the past few weeks are getting closer. They seem to be shuffling in a clumsy, stiff manner. They're clustered together, dead set on heading to our bunker.

[12/30/2160]
They're still heading in our direction, unflinching, shambling... Just what are these things? Rumors around the bunker are that they're zombies, but that's impossible; They'd freeze in their tracks if they were.

[12/31/2160]
While everyone else is off celebrating New Year's (I guess traditions continue even in the event of a nuclear apocalypse) I "borrowed" a spyglass from one of the soldiers. Sure, the spyglass is bent and dusty... But it's better than nothing, and the view is clear enough. It seems that their skin is a hypothermic blue shade, like they froze to death. However, none of their limbs are blackened or detached from their bodies. Just what are they? This requires more research. Much more research.

[1/1/2161]
Merry New Years or whatever. I've been studying these... Creatures extensively overnight. They walk in a stiff pattern, their eyes seem to be... Stuck shut or stuck open. I haven't seen one blink or open its eyes. What's more disturbing is that some of them are wearing clothes as if it's hot outside, while some look like standard survivors.

[1/2/2161]
They're halfway here and I haven't slept. They haven't stopped at all, it's as if they're in a trance... It's unnerving, to say the least. I've observed that a set number of them have quivering lips and a more fluid, natural walking pattern. It's as if they're recently deceased or slowly dying of hypothermia. There seems to be a slight discoloration of the skin underneath their eyes, or maybe I'm just sleep deprived. I'll ask another one of the scientists down here if he can cover for me for a few days and take some notes himself while I rest.

[1/3/2161]
Dr. Lieter asked me to take some notes on these... Things. Well, they're much, much closer now. More than halfway. Maybe even 3/4 of their way here. Also, Dr. Lieter was right; there is a discoloration underneath their eyes. The few that Dr. Lieter dubbed "recently deceased" have stiffened up a bit. If the others find out, it'll just enforce that superstition of 'zombies' that some of the pre-nuclear survivors have drummed up. I'll continue my research tomorrow.

[1/4/2161]
Dr. Lieter asked me to take notes again while he watches them from above with that spyglass he took from General Victor. It seems they'll reach our bunker in a day, maybe less. They seem docile, but... I don't know. Maybe the rumors are true. They've seemed to gather more numbers overnight and it's shaking all of us up. Lieter says that it'll be fine, that zombies would have just frozen due to no body heat production... Is he right? I don't know. However, I have observed that the discoloration is an odd, dark blue fluid, as I can see it drip off their faces. One of the soldiers suggested it was liquified intestines. Disgusting and doubtful.

[1/5/2161]
There was a scare about those things today. We all awoke to banging on the walls, only to find that the creatures were just... Repeatedly walking into the wall, banging on it with their bodies. Dr. Lieter volunteered to go out and see if they were hostile. If we're not all dead by tomorrow, Dr. Lieter should return and resume notetaking.

[1/6/2161]
The creatures are docile. None made any movement to attack me or lunge at me; the most they did to aggress me was idly bump into me and continue walking into the walls. I got a closer look at one specimen that seemed to be wearing sleepwear; all it was wearing was a light grey t-shirt and some rolled up black silk trousers. It had specks of freshly fallen snow in it's hair; I thought it was the temperature's doing, but... They're ice cold, although what was I expecting? Their skin is collecting frost and miniature icicles. I think I'll take one back into the bunker for further research.

[1/7/2161]
The banging of the creatures sounds like hail beating down on a car while you're inside. It hasn't distracted me from my research however, so first things first; what is that weird liquid leaking from their eyes? After studying it, it seems to be a form of liquid nitrogen. It's not composed of anything like liquid nitrogen, but it sends anything it touches into rapidly plummeting temperatures. Also, this creature is dead. No heartbeat, no vital signs, no anything. My first hypothesis is that they're in a loosened state of rigor mortis, and that the aimless wandering can be attributed to muscle memory. It seems the freezing temperatures have preserved two parts of the brain: the cerebellum and the temporal lobe, both which control movement and muscle memory, respectively. Now what I can't explain is a weird mumbling sound that they sometimes produce. I can't hear what it's saying, if it's saying anything at all and it's not just conflicting temperatures forcing the body to release any gasses.

[1/8/2161]
They're still banging, it's annoying, sure, but we're all used to it. Anywho, the bunker has came to a consensus about what we call these creatures. Some people suggested 'The Frostbitten', but I interjected that we need a solid, scientific name for this phenomenon. A person who claimed to know a bit of Latin stepped forward and proposed that we call them 'Frigore Mortis', which he claims translates to 'Death by Freezing'. It's fitting, at least. I shall do tests overnight to try and find out what that mumbling is and how they seem to preserve their below zero body temperature.

[1/9/2161]
This discovery is both fascinating and yet heavily disturbing. They're mumbling the words 'so cold'. Repeatedly, but at random intervals. I could attribute this to muscle memory, but how would the vocal cords still function? I'll get to that study later; there are more important things at hand, and that's how they preserve their temperature. I theorize it's that it is the fluid they produce, which we named 'rigentem fluidum', which translates to 'freezing fluid'. Now, to find out how they produce it... This will definitely take all night, maybe more, due to the fact that their skin is very thick. It will take a lot of force to even hope to get through even the thinnest layer.

[1/10/2161]
We found Dr. Lieter dead. Hypothermia. We can't find his test subject either. We're evacuating today, and hopefully before any other unexplained deaths occur.