[quote=Dead Cruiser]
I was thinking in terms of his metamorphosis from Shirou into EMIYA, and the cyclical nature of the Holy Grail War.I really don't understand how the Tower relates to him.
[/quote]

Because a Counter Guardian's purpose is to kill and destroy, no matter how many it is and regardless of the devastation, so that humanity survives. Ironic demise? The whole [i]reason[/i] he's so bitter is that always wanting to save people has made him an indescriminate murderer beyond comparison. Plus there's the whole 'try and kill myself in the past to break this mess' goal.

The Magician equally seems to apply to post-Fate and post-UBW Shirou, especially when you look at all its meanings.