The Deep Web in general. I've never visited that place but I've heard it's basically the Internet's sin city as it's loaded to the brim with entire websites dedicated to glorifying every kind of awful thing you can imagine
From what I've been told there are sites about the following terrors:Illegal firearms, drugs, terrorism, ISIS recruitments, human trafficking, child pornography, zoophilia, strong racism/sexism, Nazi propaganda, snuff films, videos/images of real animal abuse, fake celebrity porn manipulated to make my favorite respectable female celebrities look like sl*ts, real videos of people getting raped, sickening conspiracy theories, Holocaust denial, white supremacist forums, incurable computer viruses, vicious computer hackers lurking everywhere, and tutorials on how to kill people.
So yeah, that's more than enough information about the deep web for me to avoid that place like plague. I wouldn't visit the deep web no matter how much money you payed me.
Initially I assumed that the deep web was just a myth because I'd only heard about it on creepypastas, because I love anything creepypasta-related I decided to do research on what this "deep web" thing they keep talking about is. Unfortunately while most terrifying creepypasta concepts whether it be Slender-Man, The Rake, Caledon Local 21, Squidward's Suicide, Jeff the Killer, Smiledog.jpeg, Mr. Widemouth, etc. are completely fictional the deep web is as real as you and I.