Spook’s note contains a message to Vin, warning her about Ruin’s ability to manipulate people with a piece of metal inside of their body (a so-called Hemalurgic spike).[1]
Spook inscribed it on a thin metal sheet, knowing that only text carved in metal couldn’t be altered and read by Ruin. He discovered this ability of metal during the events in Urteau, and thought It important to warn Vin about this. Because Spook got injured during the Coup of Urteau, Goradel offered to deliver the note to Vin, who gladly did this because Vin once saved his life.[2]
Goradel set out from Urteau in the direction of Luthadel, where Vin was heading. The note, however, never got to Vin. It was intercepted by Marsh, a Steel Inquisitor, who killed Goradel after a short fight, and took the message. Ruin forced Marsh to read the message out loud because he couldn’t read it himself.[1]
But sending out the message wasn’t in vain. Because Marsh had to read the note for Ruin, he also knew it’s content. With this knowledge he was able to pull out Vin's earring with his last bit of free will, allowing her to take up the Shard Preservation.[3]
Content
“Vin, My mind is clouded. A part of me wonders what is real anymore. Yet, one thing seems to press on me again and again. I must tell you something. I don't know if it will matter, but I must say it nonetheless.
The thing we fight is real. I have seen it. It tried to destroy me,and it tried to destroy the people of Urteau. It got control of me through a method I wasn't expecting. Metal. A little sliver of metal piercing my body. With that, it was able to twist my thoughts. It couldn't take complete control of me, like you control the koloss, but it did something similar, I think. Perhaps the piece of metal wasn't big enough. I don't know.
Either way, it appeared to me, taking the form of Kelsier. It did the same thing to the king here in Urteau. It is clever. It is subtle.
Be careful, Vin. Don't trust anyone pierced by metal! Even the smallest bit can taint a man.
Spook.”