SCP Foundation

So, my first idea is for this object that causes anyone who reads, sees or looks at it in any specific sense to believe it's incredibly dangerous and must be destroyed, even though the object itself is impossible of harming anyone in any possible and is also indestructible. The irony is that object becomes Euclid due to this, as people will become so obsessed with destroying it they harm themselves and others in order to attempt to do so. The twist will be that the entry had to be written by SCP-682 to allow people to know about it without going insane, meaning the one with a violent hatred of nearly everything is the only one who can comprehend it. I might also imply it's from the same universe as 682, but I know it's a bad idea to make SCP's rely on other ones to prop themselves up. (I learned this hard with my first SCP, who was a glorious orangutan that was the child of the other orangutan in the foundation).

The second one is a guitar that can be tuned to an infinite degree of notes, including ones that humans can't hear, but will be able to due to the device. They'll permanetly hear it though, and it will turn out that the lowest and highest frequencies cause people to hear horrifying things that drive them insane.

object that causes anyone who reads, sees or looks at it in any specific sense to believe it's incredibly dangerous and must be destroyed

I think we already have lots of attempts at this. Compulsions are pretty played out these days though—maybe consider reading through the further discussion on the narrative issues of compulsion and addiction effects.

the entry had to be written by SCP-682 to allow people to know about it without going insane, meaning the one with a violent hatred of nearly everything is the only one who can comprehend it. I might also imply it's from the same universe as 682

Ehhh. Seems to rely too much on the lizard, which is kind of considered overhyped by today's community. Maaaaaaybe it might be possible as a tale, but an article that relies that heavily on someone else's SCP probably won't do well.

They'll permanetly hear it though, and it will turn out that the lowest and highest frequencies cause people to hear horrifying things that drive them insane.

Things that cause people to go insane are kind of in the same pitfall realm as compulsions. Basically, if an object forces anyone to do something or basically amounts to "it hurts people in different ways" and nothing else, it comes off as kind of boring because insanity and pain are pretty generic so far as the horror genre goes. You'll need something more unique if you want it to stay on the site.