This is a description of the spell that Harry cast on Granger.
Trahison: literal translation is Betrayal
Effects: Marks you as a betrayer of the worst kind
Makes it so the one who cast the spell is the only one who can do damage or kill the one under the spell
It's a legal spell
Very rare
Takes either a large amount of power to cast or pain so strong it over rides need for power
Leaves a mark that is unique to the castor
Harry's is a lightening bolt because it says who he was and the color of it marks the intent and shows who he will be
Color- Depends on intent and strength
Red: strongest, shows the intent to kill and torture
Black: second strongest, shows intent to make person a slave
Can make them do anything the castor wishes
Blue: pick any form of legal action without trial for betrayer
All colors show harmful intent
Had it not worked the magical energy would have back lashed and would have turned the intent back onto him. Since his intent is physical pain plus anything he wishes her to do, then he would have been killed.
Only way to be released from the spell is to kill the castor.