Shrek was having the time of his life, he was at peace in his withered-log home, scarred villagers that tried to kill him(because its a part of the fairy tale) and anyone that trespasses on his land will have to deal with the consequences.
That was something he was going to do to a princess that have lost her way unto his land, she was sitting in a sturdy make-shift cage naked and crying after what he told her 'What happens to the trespassers?'. She had never been so afraid of the aftermath of what the Ogre meant.

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Fiona struggled as Shrek carried her to a metal spit and tied both arms and legs to to pole.