"The idea of 4x Graveborn Muse in an all-zombie deck always scares me" -Ephraim

It is understandable to fear Graveborn Muses ability. It often sends you into a suicidal clock where you must kill before it kills you. However with the cards you draw in the process it can be quite easy to kill before you would die. One of the objectives of the deck is to be able to ride the power Graveborn Muse to an impressive victory. That is outside of the 4 mana cards there are a lot of low mana spells.

I do have Cabal Therapy to sacrifice the Graveborn Muse when required. I am considering replacing the 4 Crypt Keepers with 4 Carrion Feeder for additional way to sacrifice. Carrion Feeders ability is also quite useful in a deck that should be attacking with everything at every opportunity, and the low mana cost is also fits well with the deck.

As for Putrid Raptor I think a mana cost of 3 that is not lowered by Undead Warchief is a little too expensive for this deck.

I was going to post this in Legacy Development but I don't think I'm allowed? Anyways I made this deck because I'm a black mage and I know in my heart the Zombies are better than Goblins. I am aware that this deck doesn't do that well against Goblins; that is not the purpose here.

Decklist:
4 Duress
4 Cabal Therapy

4 Sarcomancy
4 Carnophage
4 Crypt Keeper (\Yixlid Jailer)
4 Withered Wretch
2 Plaguebearer
4 Graveborn Muse
4 Undead Warchief

4 Dark Ritual
4 Peat Bog
18 Swamp

Sideboard:
3 Null Rod
4 Dystopia
4 Leyline of the Void
4 Engineered Plague

Card overview

Duress: Discard is one of blacks key success factors & Duress is probably the best discard card out there.
Cabal Therapy: An excellent supplement to Duress. That allows you to sac a Graveborn Muse necessary.
Sarcomancy: A 2/2 for 1 mana that has effectively no drawback in this deck.
Carnophage: Not as good as Sarcomancy, but 2/2s for 1 still rock.
Crypt Keeper: I imagine some of you will have to look it up. It's decent graveyard removal in a pinch & a solid 2/1 for 1b.
Withered Wretch: Excellent Graveyard hate and a 2/2 for bb.
Plaguebearer: Sucks he's only a 1/1 but has a really useful ability.
Graveborn Muse: The cards this guy draws is just sick sick sick. He really just overpowers your opponent.
Undead Warchief: I read that when R&D were testing the set he was a 0/0 for 1bb with the same abilities. How nice that would have been. Still crazy powerful though.
Dark Ritual: Excellent acceleration. Really speeds up the deck.
Peat Bog: Nice acceleration, speeds up casting the 4-mana bombs.
Sideboard: Just a collection of cards that hose certain decks.

Yixlid Jailer: Did not make it in because it freezes Cabal Therapy when you need to sac your Graveborn Muse.
Grave Defiler: Not as powerful as Graveborn muse. The deck has a lot of non-zombie cards.
Rotting Giant: The best of the 3/3 zombies for 2. Could replace Crypt Keeper.

The deck looks standard enough but when you draw 5 off your Graveborn muse, duress & therapy away your opponents hand, drop 3 Zombies including a Undead Warchief, all in one turn, you might see some potential.

Let me know what you think! I play more T1 than legacy so I ready for criticism as well.