Yeah y'know! Smokey's defo one hell of a complex character!!
I don't know about mannifesting its self into solid living creatures but do think it can some how scan minds & lock into their memories....
Like the Eko incident!
I've always thourght that the visions some of them have had was somehow down to the strong magnetic pull sending out waves & effecting their brains?........so.......I might be wrong but i cant remember anyone seeing things they shouldnt since Desmond turned that key!! (Apart from Sayeed n the Cat) & thinking about it, if i'm right then Rose will start getting ill again unless the Magno forces completely cured her??
Sooo Many Mysteries & Questions but not many answers!!!
For every mystery that's revealed another 5 take its place!!

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"Where i come from,...I just dont come from!" HARD-FI