Rat's Nest with Corrupt: Cast on critical strike.? WTF IS THIS

I have a link to my other forum for trading here: https://www.pathofexile.com/forum/view-thread/2050503

Regardless, what is this and is this valuable? I know CoC was nerfed quite a bit recently enough but this is still INSANE! What is this worth, even a guess.. It's nowhere, I've looked everywhere and I've seen nothing like this ever.