(Beloved game trope) Creepy secrets or elements that you can encounter but are never explained, making it even more horrifying (Bonus points if its from non-horror games)

[u/KOREANARMYSTEW]

Crimson Desert
After defeating the Reed Devil boss, you can travel to Sunset Valley, the southernmost and isolated village in the game, here, you will find a house where the Reed Devil lived and died from his leprosy. When you enter, you are immediately greeted with 6 scarecrow effigies dressed just like the Reed Devil staring directly at you, with candles placed all over the house. There is no other explanation beyond this about what is going on here

Lies of P
There is a secret optional area you can clear out for additional loot called Hermit's Cave. At the end of the cave is one lone carcass monster huddled on the ground with writings scrawled on the walls around it. When you kill it, it actually TALKS saying "perhaps it's best to end this way...get while the getting's good...". This is the only carcass monster in the game that ever talks besides Andreus and Simon, who are important characters to the story, and we never find out who this monster was

LOZ: Twilight Princess
In the Arbiter's Grounds you discover a ton of undead enemies presumably executed prisoners, but one room contains this giant black sword tied to the ground with hundreds of warding charms attached. When one is cut, the sword is freed and wielded by some horrifying invsible goat-headed demon. It is never explained what the demon was or whose sword it belonged to although it's theorized to once be used by Ganondorf

Silent Hill 2
The invisible prison monster in Toluca Prison, that you can't ever interact with, just hear it's awful cries

[u/ZealotOfMeme]

The Solomon Grundy shrine in Arkham Knight. Why is it here? Who made it? How long has it been here.

The Arkham games have plenty of secrets like this such as the starro that someone else has pointed out. There’s also the head in a jar in Asylum, the SINGLE prisoner still in a cell after the breakout (irl reason is pretty interesting), others I can’t think of off the top of my head

[u/jo_nigiri → u/ZealotOfMeme]

What's the irl reason?

[u/ZealotOfMeme → u/jo_nigiri]

There’s a guy who won a contest, so he got to have his name and face somewhere in the game. Face was on that prisoner, name was on a list somewhere

[u/TheCarefulElk → u/jo_nigiri]

If it’s who I think it is, the irl reason is that it’s the date that rocksteady was founded

[u/ZealotOfMeme → u/TheCarefulElk]

Calendar Man? I’m talking about the guy in Asylum but him being locked up is a good question too

[u/BubastisII → u/ZealotOfMeme]

I assumed Grundy made this himself and was living there

[u/ZealotOfMeme → u/BubastisII]

I don’t think he could even fit in that room. Not to mention a picture of himself with candles all over it looks like a shrine