I'll be surprised if we get any explanation that's satisfying.  Well, beyond a long internal monologue by Dresden that rests on a foundation built on a reading of 'All You Need is Love.'  I'm not expecting the readers will get anything close to an explanation of how the universe Butcher has built all works and comes together logically (even one that's at the descriptive/predictive/Newton level and not at the fundamental/'why does it work that way' level). 

After Twelve Months, I have a creeping feeling that the conclusion of the Dresden Files will reveal that the entire series was 'True Love Conquers the Outsiders.'  If that's all there is, then let's just keep reading and hope for a rollicking, enjoyable remainder for this yarn even if at the end we're left with a lot of Lost-esque unresolved loose threads.

In the aftermath of PT and BG, a lot of Carlos hate was thrown around on this site and others, Carlos is blind, dump, should trust Harry etc, etc. In the post 12 Months discussion there is little being said about Carlos and Harry interactions ,and Eb and Harry's interactions.

Nemesis is the Outsider He Who Walks Beside.