Jason is not evil, rather, misguided.
Or this is what his parents like to think.
Jason likes to think of himself as a pure Slytherin, although unbeknown to his fellow students, he has what he describes as a weakness, he has a heart. He is 15 and very competent with his magic.
Jason is determined, his hero is Draco Malfoy. He is pulled by Draco's weakness yet Draco has a devilish side. Although he would rather not admit it, he is rather scared of who Voldermort was and is afraid that something like this would happen again and although he would not like to admit it, he would not mind being the next Voldermort - though he may have a slight problem with the killing and conscience part.
Portal 
