I personally don't see what's wrong with the character.... his connection to Morpheus isn't that much of a deal in my opinion, especially since it more or less reminds me of the demigods from the Percy Jackson series (who could still get whooped despite their heritage). The only problems I'd see that could arise is the potential for godmodding with the whole using anyone's blood to control or kill them from the inside. That, and the fact that the Morpheus abilities seem to be capable of freeforming, but then again, what magic isn't? So long as it has it's counters and limitations it should be fine.