Moonsilver Spear might be up your alley for this deck.
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Put lingering souls in for midnight Haunting and splash a little bit of black. And possible Rootborn Defenses for eyes in the sky, at least 1 or 2. I take that back Just don't use Eyes in the sky and run 2 rootborn and 2 midnight hauntings. You might want to rethink Divine Favor as well for something a little more substantial or at least renewable.
Yeah I though about that but I couldn't justify adding more artifacts that would just be mildly helpful.
You may want to look at Tezzeret's Gambit for some draw power and proliferate.
Nice, I like it. My only suggestion might be replacing the spellbooks with something else between 2 towers and 4 Library of Leng's they are a little redundant. If nothing else replace them with 2 more towers so you can at least get land out of it, just my 2 cents.