Correct me of I am wrong, but after taking Senkas blood, Declan could barely do magic, and when he did the healing effects stopped or lessened right? Was it clarified if this was because he still had injuries or simply because her blood was in his system? It wasn’t like he could switch from on to the other, so just the blood being in his system caused issues right? I think it was days later that he was teaching the class and struggling, he was pretty much healed by then as well. It would be the same thing back in college arcane, even if he had no injury at all, he used the blood RIGHT before training in magic and it did heal him, he still struggled at the buffet when he took his arm slings off and discovered he was mostly all better in demon divine. I will have to go back the demon divine and check the senka blood part but please let me know if you remember how it worked exactly.
I really like the idea of magic being his vampire ability. Maybe a temporary loss in magic as he is first changed and it grows with time? Some magic resistance as well? Even if he can only do a little bit of magic, his amulets that connect to elementals could make him almost on the same level. I do think Tanya should change someone at some point so we can see what happens. I bet when Tony grows up she would be a candidate.