Threat: When not visible, corset strings […]
Here's a concern I have. Perhaps this was just an stylistic choice of yours to separate the description from the effects, but it gives the impression that you think SCPs must be dangerous, which is not true. There's nothing wrong with wanting to go for the old archetype of "killing item", but the simple "this is spooky because you won't suspect it'll kill you untl it's too late" has been covered a lot and won't impress readers unless done really well. For example, take this (admittedly not too recent) skip about a watch that ends up with people covering themselves to death, which stands at a not too good but not too bad +67. Why? Because it paints a weird picture that grabs the reader's attention.
Backstory: Commissioned in 1854 by a noblewoman named Isabella Fitzpatrick, crafted by Angela Brehm. Stolen from Isabella by a woman named Marjorie Hamilton, who was found dead wearing it. Returned to Isabella, who was also strangled by it. Buried after Isabella's death. Found in 2013 by Johnathan Kennedy.
This is… alright. Not particularly gripping, but not terrible. However, you must think of the important bit: how did the Foundation learn this stuff happened? The wrong framing device can kill an otherwise good story if it breaks suspension of disbelief too much.