Contaminated Ground seems to be a bit out of place in this deck.

+1 for getting into magic!

When you get more cash and cards, you'll want to fix your mana base so I would say -3Orzhov Guildgate -1Swamp and +4Godless Shrine

I would also drop some of the one-of cards to a better draw. Remember when playing Extort you're going to need the mana to use the ability as well.

That being said, let's start off with some small tweaks. (Just my random thoughts and opinions, so take as a grain of salt)

-1Knight of Obligation -1Contaminated Ground -3 Dying Wish -2 Daggerdrome Imp -1 Shielded Passage

That gives us eight cards to add, so maybe focus on the removal of creatures and killing them with lifelink. In later rounds you'll be able to trigger your extort as well for casting those cards.

+2 Tragic Slip +3 Devour Flesh +1 Vampire Nighthawk +2 Vizkopa Guildmage

On their turn, play Devour Flesh , then trigger morbid with Tragic Slip . Yes they will gain some life, but they probably won't kill a high powerful creature.

On your turn trigger Vizkopa Guildmage 's second ability and swing with your Vampire Nighthawk or a creature enchanted with Gift of Orzhova . As the rounds get longer you should have enough to cast a card and extort while the ability of the Guildmage is on the stack.

Your 4 Murder vs Ultimate Price is a never ending battle. I would suggest you sideboard one set of them and change when needed.

Again, as you keep playing and getting cards you can throw in more expensive rares and mythics to throw in and use.

As a more permanent answer to drawing more cards you could consider Underworld Connections . People argue a lot about whether it's better than Sign in Blood . I'm not sure. I know that if you're going for the long game Underworld Connections can let you draw more overall.

If you can get ahold of them, Obzedat, Ghost Council works really well with extort.

Because all your creatures other than Treasury Thrull and Obzedat, Ghost Council are rather small, I think you'd get more benefit by replacing Nearheath Pilgrim with 2 more copies of Lingering Souls. It will help you stall the game more effectively and will give you even more opportunities for Extort triggers.

You mention wanting better card draw, and because this deck wants to play a longer, more drawn-out game you'll end up getting a lot more cards from Underworld Connections than you will with Sign in Blood. If you don't care about keeping the deck Standard-legal, then go with Phyrexian Arena instead.

Other card draw suggestions I can think of would be Bloodgift Demon or Altar's Reap (I quite like doing this on a Doomed Traveler, then if you have a spare Tragic Slip to kill off one of the opponents creatures, then happy days!)

I agree with the extra Lingering Souls, I'd be tempted to add Blood Artist's, most likely in place of the Guildmage. know there's the whole infinite combo with Exquisite Blood..but..that's up to you. I agree it's a bit of fun and awesome in multi-player.

Blind Obedience would fit the deck nicely, if you can get a hold of some. Here's my Orzhov deck should you wish to take a gander, provide suggestions or get ideas Obzedat and Friends.

All the best and good luck.

i also agree with Rhadamanthus i'd also suggest removing a copy or two of Vizkopa Guildmage for Blood Artist.

i'd also drop Murder for something cheaper like Dead Weight or Bone Splinters.

i've also found that Vault of the Archangel is pretty much a dead land. it costs 5 lands to tap for its ability to function.

might switch out the Oblivion Ring for Pacifism. i feel that in this deck, creature removal is what you use it for anyways. but i could be wrong.

not a bad extort deck though all in all +1

Bone Splinters is an awesome removal card (again in conjunction with Doomed Traveler, but useful with Lingering Souls too)

Drop Vizkopa Guildmage, add in at least 1 more Obzedat, Ghost Council if you ever want to draw him and add in at least 2 Rhox Faithmender. +4 of both Godless Shrine and Isolated Chapel. I'd drop Mentor of the Meek -just seems slow/costly. +1 Sorin, Lord of Innistrad -1-ofs are typically useless unless they are a secondary card that does the same as another of in your deck. Bring Vampire Nighthawk up to 4. And then I'll leave your extort creatures alone since that's what you want your deck to be based around.

Check my orzhov deck for reference (the original version looked a lot closer to yours, but it's a reference nonetheless: Dead life (Orzhov Midrange ) -suggestions needed!