Built around Heartless Summoning. This deck abuses that enchantment in several ways, by either powering out fatties or having a kind of combo with Havengul Lich and Perilous Myr. The side board is not 100%, I need some help on it.
Unlike other Hertless decks decks, this one is designed to be able to work with either only a single Heartless Summoning, or two out. While there are two out Solemn Simulacrum becomes a 0 cost Rampant Growth
+
Reach Through Mists
. Pair that with Havengul Lich and you can draw X cards and search for X basic lands for !
I decided that maxing out on my potential to draw the deck's namesake Summoning is important, so I added what I consider to be versatile Summoning 5-8, Muddle the Mixture. It can search for Heartless Summoning if I need it. It can also search for a fattie, Myr Superion, if I already have a Summoning out. If I am going for the "combo kill" it can also grab Perilous Myr. Lastly, it does a pretty good impression of being a Counterspell.
Shriekmaw and Mulldrifter are both awesome in this deck. Summoning reduces their evoke cost, so you can have both of their effects for either a or a respectively. Additionally, they can both be cast for their evoke costs from the graveyard with Havengul Lich so I can just keep the fun going again and again.
I really think that Lodestone Golem shines in a deck like this. He can be powered out as early as turn 3, he will still have an impressive 4 power even with Summoning, and he will dramatically slow down or even stop our opponent entirely. Also our cost for playing him is mitigated by playing a lot of artifacts and by having Heartless Summoning.