There is another spell with mana value 3 or less on the stack.
({2} magic symbol) ({U} magic symbol) available.
Steps
Cast Mesmeric Glare by paying ({2} magic symbol) ({U} magic symbol) , targeting another spell with mana value 3 or less currently on the stack.
Gorion triggers, copying Mesmeric Glare, with the copy targeting the original Mesmeric Glare.
Resolve the copy of Mesmeric Glare, causing you to exile the original Mesmeric Glare, and cast it from exile without paying its mana cost, targeting another spell with mana value 3 or less due to Guile.