Motif 

A motif of Mistborn by Brandon Sanderson is Descrimination. This is because throughout the book Vin and Kelsier have a reoccuring hatred for the slavery of Skaa. One reason for this might be because they are half blooded Skaa too. We see acts of kindness in Mistborn by Brandon Sanderson too. one example of this is when the Skaa are allowed to rebel. they gather in the caves as a resistance to the Lord ruler. In fact, the entire plan made by Kelsier is to free the Skaa from slavery. so in the end Vin killed the Lord ruler to save the Skaa.