All that aside, a good person would not kill Grelod, it's really that simple. I've considered a lot, and murder is not an acceptable solution to the problem in Riften Orphanage. If you think so, I believe your moral compass might be a little off (think as in, if this were real life, it'd be alright). The Dark Brotherhood being only the instrument of killing, and therefore not evil is total horse manure. They're a bunch of sadistic killers, plain and simple. Hasn't stopped me from joining them though

