I came back to get revenge

A world where angels and demons used to have mediators between them . "DEIGO" this mediators keep the world at peace . But 30 years ago , a mediator turned evil and joined the demon side. What followed was a bloodbath and a war that shook the 3 realms. Atleast the evil one was killed by none other than her own teacher and the region of terror was vanquished. Now 30 years later, Arissa woke up in a poor excuse of a room and dead body on top of that! And what's with this 10 foot long revenge list??