Everyone treats Spook like he's dead, but given that he supposedly ruled for a century post-Catacendre, he was granted full Mistborn status by Harmony, and that he was assisting Kelsier with Hemalurgic stuff, would it be a safe bet that he is still alive? Brandon has said this, after all:
He could have, in order to assist Kell further through the time needed by spiking someone's atium Feruchemy and compounding that forever (a la TLR). I kind of hope so, I like Spook.