I remember when I first discovered these odd entities. It was a normal day. I was trying to play casual in TF2 like usual, trying to avoid hackers and such. Despite me trying to escape the bots, they were practically in every server I connected to. In my despair, I tried to play some community servers. I scrolled and scrolled until I stumbled upon this one Upward server. There was something... odd about it.
The server had no name. 0 players too. I tried to open up the server info page, but it was blank. Then I tried connecting and that actually worked. I joined RED, having not played defence in a while. Surprisingly, the game was already starting. The gates were open, the timer was running. Something was wrong and I could feel it, yet my morbid curiosity forced me to stay and find out what the hell this server is.
I walked up to the 1st point as the Sniper, taking my position and checking the gates. No one was there. I scoped out and got up to the gates, trying to check BLU spawn. No one was there. "What if I go to the last point?" I thought. This was a thought that I wish I never had.
I remember it clearly. I was walking on the bridge below the 4th point, dead quietness in the air. I walked past the health pack, up the stairs and into the exit. And that's when I saw... IT.
Massive head the size of a watermelon, maddening eyes that look at you no matter where you go, and a terrifying respirator that looks like a snout. The combination of these three elements make this monster look like a giant alien mosquito out to suck you dry. Having already been freaked out because of the absence of the server name and the game starting despite there being no players, I tried to leave the game immediately. When I pressed ESC, I found out that the "disconnect" button disappeared, and I was left all alone with this... Creature.
When I exited the pause menu, it was no longer there. I immediately ran to the last spawn of Upward, hoping that the monster won't catch up to me. To my relief, it didn't. I'm sitting here and writing this in hopes that if someone encounters the Creature, they will leave the server they're on immediately.

I've spent a few days on this server already. I can't shut down this game by force and I can't turn off my computer. Something is severely wrong.
I also found out that that monster wasn't the only one here. There's more of them. But anyway, I feel a lot more relaxed now, since I found out most of the Creatures don't actually attack me. They just... watch. They're still unnerving but I have a lot more confidence venturing out into this Upward. I really need to get the hell out of here.

I'm starting a... sort of bestiary to help me better understand what kind of entities these are. I'm going to share it with you.

1) The Hunter Creature

This is the most common type of Creatures. As I've seen in the notes scattered around this map (some of them look like angry chat messages, some look like weird drawings, some contain cryptic messages, I don't really know how to describe them properly), this one is very dangerous on casual servers, as it's typically seen running around with The Phlogistinator, The Scorch Shot, and The Powerjack. What makes it even more dangerous is that they're commonly seen with a pocket medic, making the extermination via phlog even easier than it should be.
From the looks of things, that giant head I was describing earlier is the fuel storage for the phlog, since it wobbles around too much when the Creature moves. The snout-like respirator helps them consume food faster, and the eyes provide them with 180° vision.
Curious note I found while looking through this map:

So someone was there before me, huh? Interesting...
Looks like I was compeltely right about the respirator and the fuel storage. But I didn't know their brains were this small. Curious.
Threat level: Low

2) The Female Creature

The most noticable difference between this Creature and The Hunter Creature is absence of the snout. Instead, The Female Creatures have something that looks like giant claws in place of a mouth. As I've seen in the notes, they use those claws to tear out the male's respiratory snout and brain, the reason being: in the very end of the snout males have their DNA stored. They fixate the male's brain and his snout inbetween her claws, then both of the brains in her body and the claws die to serve as the nutrition for the fetus. After that, both parents become something called The Awakened Creatures. Weird stuff.
Threat level: Low

1) The Cleaner Creature

Sex: Male
Team color: Red
Eye color: Black
Very aggressive. Notes suggest this one was one of the most dangerous Creatures to ever roam casual servers. As the name suggest, it uses it snout not as a substitute for mouth, but as sort of a makeshift vacuum cleaner. It sucks up everything from the ground, and if you stand in its' way, it will try his best to consume you without actually eating you. As far as I'm concerned this is how all Creatures survive: by consuming food. And that food can be somone alive. I can't believe I can describe something like this without actually feeling anything... this world is doing something to me, and I don't like it.
Threat level: High

2) The Poisoned Creature

Sex: ???
Team color: Red
Eye color: Yellow
This one is aggressive as well. Instead of a snout, The Poisoned Creature has a tube that connects its' mouth to... something that looks like a small cistern. As the notes say, something that's called "The neverending supply of Citrus" is stored in there. I wonder what that could be. So, wait... it doesn't need to eat, since it has that supply. But that means... Oh, God... It kills just because it can.
Threat level: High

3) Baby Creatures

Sex: Male/Female
Team color: Red/Blue
Eye color: Red/Blue
The result of the reproduction. Nothing much to say, except they're much smaller than your average Creature and their snout/claws are replaced by an actual mouth this time. how cute
Threat level: Very Low

4) The Brainlet

Sex: Male/Female
Team color: Red/Blue
Eye color: Any
Just a Creature that ran out of fuel for the phlog. Doesn't seem to be dangerous.
Threat level: Low

5) The "Nyarlathotep"

Sex: Male
Team color: Blue
Eye color: White
The most interesting out of all the uncommon Creatures, to say the least. Surprisingly, this one is revered as a god in the notes, hence the name. From the looks of things, this is the embodiment of all Creatures and their will personified. His multiple snouts, which can be fused or unfused with his body at will, help Him him eat more efficiently than all the other Creatures.
I have found... something interesting attached to the image of him I found. A note. This is what it said:
"IT CAN'T BE BARGAINED WITH. IT CAN'T BE REASONED WITH. IT DOESN'T FEEL PITY, OR REMORSE, OR FEAR. AND IT ABSOLUTELY WILL NOT STOP, EVER. UNTIL YOU ARE DEAD."
Something is wrong. Something is wrong. Something is wrong. Something is wrong. Something is wrong.
Threat level: Very High

6) The Messenger

Sex: Male
Team color: Red/Blue
Eye color: Brown
It has a mouth, but I've never seen it eat. It only... looks at me from a distance. When I tried to get closer to it, a weird sound appeared in my head while it kept staring at me with those three nightmarish eyes. Pop... Pop pop... Pop pop pop... The closer I go, the more unbearable this sound becomes. ShPOPit, I can feel it boiling my brain. I found a couple of notes that suggest these are the messengers of The "Nyarlathotep", saying how "The eyes of The Messengers are His eyes".
Threat level: Average

its been 12 days im still stuck in this place although i dont feel uncomfortable or scared anymore something is happening to me i feel at peace why do i feel at peace why why why
i can tell this is going to be over soon over over voer voer over very soon
while im still alive i will try to describe the process of a process of a creatures awakening the best i can

stage 1:

sex: Male/Female
team: red/blue
eyes: white
as i've said previously the awakened creatures start their birth at the same time as the fetus
the female fixates the males snout and brain in between her claws and this amalgamation serves as the egg the egg the egg the egg for the baby
when its fully nutritioned and ready it falls off of the females body soon after the baby is born is born and the parents begin to mutate mutate mutate mutat eatm uat mutatr mutea muteat mutatae mutae mtamar amt muate
threat level: help me
stage 2:

sex: No
team: red/blue
eyes: orange
when the holes in the parents heads start to mutate the outside of those mutations mutations hardens up and acquires a pretty yellow color
it looks like a maw
i want one
threat level: RUN

i finally found out whats happening to me ive encountered two of the awakened creatures and accidently let them touch me at some point before i didnt mind much they werent aggressive at all i just accidently brushed past them and they looked looked looked looked looked at me this is a mistake this shouldnt have happened i can feel my brain brain brain corrupting i can feel my snout mouth mutate something is growing growing on my head i cant take this anymore i cant i cant take this anymore i cant take this anymore i cant take this anymore i cant take this anymore i cant take this anymore i cant take this anymore i cant take this anymore i cant take this anymore let me go let me go let me go LET ME GO IT HURTS IT HURTS IT HURTS IT HURTS PLEASE STOP IT HURTS SO MUCH IT HURTS

OH GOD.
THEY ARE BACK.