Spook, or Lestibournes, is one of the original members of Kelsier's crew. He appears in all three books. Spook's name Lestibournes is translated from street slang to "Lefting I'm born", meaning "I've been abandoned", as Spook's parents hated him because of his Allomantic abilities. The name "Spook" is given to him by Kelsier.
Spook is a Tineye, and Club's nephew. He has an incredible respect, even worship, for Kelsier. He always speaks using street slang, causing many unusual situations throughout the series. In the third book Spook also becomes a Tineye Savant, and wraps a piece of thick cloth and glasses over his eyes.
Spook has expressed romantic interest in Vin, and other female characters in the series. He is sent to spy on the rebellion in Urteau during the third book. Here, he receives an impromptu Hemalurgic spike and gains the ability to burn Pewter. Ruin influences the boy, making him think Kelsier is telling him to do things. At the end of the Hero of Ages, Spook becomes a full fledged Mistborn.
Spook is a fairly notorious character in the Faith of the Survivor. Apart from being one of Kelsier's original crew, he gained the title, "Survivor of the Flames" for his near-miraculous actions in Urteau. Although he was almost ignored in the original crew, he plays a pivotal role in the uprising in Urteau, leading the team according to the directions of Ruin, disguised as Kelsier.
Although Ruin had major influence on Spook, he later broke from its chains by removing the Hemalurgic spike from his arm, and therefore sacrificing his ability to burn Pewter - after that, he has been able to send an important information about Hemalurgy via Captain Goradel. The information was later found by Marsh, as he killed the messenger, but it gave him a hint that Vin can be saved by removing her earring, which, as Sazed later points out, saved them all.
In The Alloy of Law, set 300 years after the events of The Hero of Ages, it is hinted that Spook became the character the "Lord Mistborn" and instrumental in bringing together the new empire. Most allomancers are descended from his line. Eastern Street slang has now become archaic, convoluted High Imperial.