Impish charater of the "Song of Fire and Ice" trilogy by George R.R. Martin. Brother to Jamie Lannister, Kingslayer. He has never been looked at favorably by his father as his birth contributed to the death of his mother. He is the hier to the House Lannister because his older brother Jamie, "took the white", or became one of the King's Guards, and this means that you give up rights to all inheritances. Tyrion's father still considers Jamie the hier and will not recognize Tyrion as such.
Tyrion is a complete character and it is difficult to tell if he is good or evil. That could be the appeal for these books as the line between good and evil is so blurred.