All Hail the New Flesh (Day 17)

I've come down to a pretty solid first draft for my W/B Extort deck and have tested it a few times against a friend. I still haven't ordered any physical cards, but I have been using OCTGN to run tests. Here is my current decklist.

• Thrull Parasite x4
• Basilica Screecher x4
• Crypt Ghast x4 
• Syndic of Tithes x4
• Tithe Drinker x4
• Banisher Priest x4 
• Celestial Flare x4
• Imposing Sovereign x4
• Obzedat, Ghost Council x3
• Pontiff of Blight x3
• Swamp x9 
• Plains x9
• Vault of the Archangel x4

My first few test runs have indicated a problem with my mana base. I have a two color deck with all single color lands. This might not be an issue if I didn't have several cards with WW or BB in the mana cost. Obzedat, Ghost Council is the largest offender since it costs 1WWBB. I'm definitely going to have to include some dual lands--preferably the less expensive variants. I don't think I'm quite ready to drop $7 for singles right now. It looks like my main options are Orzhov Cluestone and Orzhov Guildgate. I might go ahead and throw out one or two of my basic lands (preferably plains since I have Crypt Ghast) and put four-ofs of both of those cards. Could potentially be overkill, but that remains to be seen.

Crypt Ghast has proven to be pretty powerful, especially if I manage to draw a lot of early swamps. Banisher Priest has been invaluable, but so far Celestial Flare is underwhelming. It's rare that I have the WW needed to use the removal spell successfully but smoothing out the mana base may change that. My best case scenario win condition for this deck involves laying down Pontiff of Blight with Crypt Ghast out. On the next turn, I'll put down a cheap creature (like Thrull Parasite) and pay for all of my Extort triggers with black mana followed by an all-in attack if need be. If this is my primary win condition, I wonder if Vault of the Archangel is even needed. I imagined it would be a good alternate win condition (deathtouch and lifelink to all creatures for four mana) but it doesn't seem very impressive with all of the low power creatures in my deck.