This is a theory crafted Orzhov deck, ripe for possible improvement into the pro tour scene with Battle for Zendikar upgrades.
The soonest you'll be able to do any damage is your third mana step, till then- you'll be using cards like Silkwrap, Suspension Field, as well as Banishing Light to nullify any early game efforts. Getting these cards out early is nice because it'll get your Blood-Cursed Knight out with life link and that extra 1/1 out right away; however its important to note that these cards are essential in the later game too. They'll protect you from big creatures, such as Dragonlord Atarka, and will be nice dudes for when Starfield of Nyx gets going.
The first creature you should put down if you can is Blessed Spirits. These little guys get huge if they can survive, and become a massive threat if not dealt with- you should want them to get big ASAP.
Blightcaster should prove to be a good way to remove little guys that are bothering you, Elvish Mystic Is a great target.
Blood-Cursed Knights may often be your way to survive the early game until you roll. The life-link on them is gonna be really useful in keeping your head above the water. They can be mega bothersome to your opponent, as they should usually be coming out swinging every time you play them. If you don't have a Blessed Spirits in your hand at the 3 step, this guy is the way to go for sure.
Enlightened Ascetic Is one of your fail safes. This guy is your abort button if you run out of time on your Demonic Pact. He's also useful against the opponents high threat enchantments, like Sphinx's Tutelage, or against nullifying enchantments like Pacifism.
Something that should be emphasized about the way this deck uses Demonic Pact, is that playing these cards in this deck is usually an all or nothing scenario. Playing them in your game is gonna yield high risk, and usually very high reward. Putting in more "safety nets" so-to-speak isn't an awful idea, and might better suit your play style. But using more safety nets means you have less power. Putting down your second pact should be the beginning of the end for your opponent.
Virulent Plague goes in against Goblins and Thopters. I would suggest siding out Sigil of the Empty Throne for these for obvious reasons.
Hallowed Moonlight Goes in to counter Collected Company, as well as Dragon Fodder
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Hordeling Outburst
(This is a meh card for me right now, very open to alternative suggestions on this one)
Infinite Obliteration goes in against Abzan, it is no fun dealing with Siege Rhino, so you might as well assure that you never even have to.
Tainted Remedy also goes in against Abzan. With this enchantment on the board, Siege Rhino becomes much less effective, and Feed the Clan becomes outright impossible to play.
Drown in Sorrow is a good board wipe against Elves or Goblins, and it wont kill any of your important guys.
What you side-out for these cards should be based on your personal preference and play style.
