I've red the previous two chapters but I still don't get why The Orc King was killed? And why? I feel that part needs to be clarified a bit.
All that's important to know is that the wizard Faramor killed the Orc King. The motive is unknown and, while much of his character will be revealed throughout this story, he will remain an enigma well into the MMORTS campaign storyline.
Just know that not all is as it seems.