This deck is a bit of an old one and allot of cards could probably be replaced by better ones but its proven to be quite a solid deck against more recent decks.
There are a few combo's and concepts I have placed into this deck.
Keeper of the dead.
To use this card efficiently you need to be able to control the graveyard, this is what scrabbling claws is for, also consume strength is helpful as it removes one creature and pumps up another that you can take with the Keeper. You also need to be able to change creatures colors, this is what scuttlemutt is for, not only does it produce mana, it can change a creatures colors for the Keeper to take.
Thinning through Land Grab and color fixing.
I wanted spells that can grab more lands, spells that play more lands and cards that could produce mana outside the color pie. Once again scuttlemutt fills this niche well. and grabbing lands and playing them for almost free lets you thin the deck out. It is also helpful to be able to shuffle your deck if your playing against any sort of deck manipulation.
Creatures are mostly to stall, Kami is great in this for reach, combined with trapper and abomination you can hold back a rather large army, combined with trapper you can groom your opponents creatures so you destroy the creatures you cannot handle and you hold down the creatures that you want to steal.
Sisters of stone death is the main centerpiece of this deck.
Once you have a large sum of mana and sisters out you can all out attack and steal plenty of creatures. First you want to remove them all and only bring them back when you can afford to or when you need to to survive, Having access to colors outside of B/G can really open options up to what you can do with your opponents creatures.
The secondary strategy to this deck is to use the Scythe on a creature to pump it up and defeat your opponent. the two top candidates for this is the abomination and the nighthawk. you can consume to pump up the creature and you can use Keeper's and trappers to manipulate what creatures your opponents can block with, they will either be forced to block with the creatures you want and lose them to you or take the damage.
The last part of this is for me to talk about the underrated cards in this deck.
Scrabbling Claws
People tend to underrate this card because the tap ability forces your opponent to choose what card to exile from their graveyard.
If this is out early, you should be able to keep their graveyard almost empty enough for the keeper. but don't forget you can also sac it for 1 at any time, choose any card to exile, and draw a card. The fact that this card stays on the battlefield and lets your opponent know that you can remove any card you want from the graveyard will change how they play the game. Think of edrazi or any graveyard based deck you've played against, this card can be dam annoying for those to the point that I have opened with two of them in my hand and my opponent with a graveyard based deck gave up after I showed him my hand.
Scuttlemut,
Not only is it great for mana fixing, producing extra mana, its can color change, working great with all the other cards in this deck, its also a 2/2 creature and can attack and block. allot of people forget this.
Twisted abomination.
This card is very underrated by allot of people who have seen me use it. It's expensive for 6 mana, but it is a 5/3 with regenerate, this makes it great for putting pressure on your opponent. however the other ability is cycling. Picture this. its turn 5, Keeper is out, your low on lands, you have 2 creatures in your graveyard, your opponent has one in your graveyard and a creature you need to cill on the battlefield. you can cycle the abomination for a swamp and now you can destroy another creature.