reya

if you feel like doing something crazy just drop 2 Bronze Bombshell's and 2 Rust Elemental's for 4 Levelers and bounce one of them to your opponent the round you play it => your opponent will lose at the beginning of his next term

nice idea that i havent thought of so far.. though i'm not gonna add him as this deck is especially fun in multiplayer and you'd lose just on your next turn... however for a normal deck it's definitely an idea to exchange Bronze Bomshell for Leveler

well Dark Ritual allows you a reanimation on turn 1, but besides that it allows you 3 Demigod's on turn 2 which is - i think - his intention here by playing a buried alive asap

as the two have already mentioned you need to ensure to get Siege-Gang out asap (e.g. with Warren Instigator or Brightstone Ritual) and you need to make more out of the hordes of goblins you'll have (e.g. Goblin War Strike, Goblin Chieftain, Goblin King, Reckless One)

and animate dead ;)
but you're right it's quite a decent chance. and if you're looking for another way to benefit of putrid imp i'd recomment my favorite reanimation spell victimize. (which is of course not just awesome in combination with putrid imp but generally, especially after buried alive) - though it was unfortunately not in graveborn

just for clarification: i forgot cabal therapy which will also enable you to reanimate on turn 2 ;)

Putrid Imp is a 1 drop, while Sickening Dreams is a 2 and Last Rites even a 3 drop; more importantly you can use Putrid Imp as often as you want to!
apart from Entomb, Putrid Imp is the only way to reanimate a creature on turn 2! buried alive and Last Rites won't enable you to reanimate anything before turn 4, Sickening dreams not before turn 3 - that's a huge difference!

i have to agree with ESPRcon, Putrid Imp is the best discard option ever. he is not in there as a threat but to ensure you've actually got something in your graveyard to revive. he's doing that a lot better than Last Rites and still a decent amount better than Sickening Dreams.
Diabolic Servitude is too expensive and even besides the cost I really don't like it because it exiles the reanimated creature as soon as it dies and thereby preventing you from reanimating it ever again

in case you're looking for further inspiration, here's my reanimator deck that is also based on the graveborn deck (apart from the reanimator targets):
http://www.mtgvault.com/ViewDeck.aspx?DeckID=259730
(i'd also be glad for any comments/suggestions)

you've got double cleave in here twice

Urborg, Tomb of Yawgmoth

i know they aren't completely similar to the others though Bladewing the Risen and Karrthus would fit in here quite nicely
also: why 4 llanowar elves but only 1 bird of paradise?

just a couple of thoughts:
- given that Visara is legendary you might want to exchange 2 of them with Avatar of Woe
- Demigod of Revenge's ability only triggers when you play him, not when you resurrect him and i'm not sure you want to wait until you've got 5 swamps out to utilise him
- personally i dont like reanimate and as you've got reassembling skeletons in here anyway you could exchange some of the reanimates with victimize
- remember you don't need to keep it black if you're gonna revive your creatures anyway. awesome reanimator targets are e.g. Iona, Shield of Emeria; Blazing Archon; Elesh Norn, Grand Cenobite, Jin-Gitaxias, Core Augur or even Sheoldred, Whispering One

quite a decent goblin deck, but what's the purpose of Goblin Fireslinger in here?
you might want to exchange it with either Dragon Fodder, Goblin War Strike or Reckless One

this is awesome. the only suggestion i have is to consider goblin war strike instead of lightning bolt, though i can understand why you might prefer lightning bolt if you want to get rid of certain creatures

but he needs to survive until phage is out

yeah i saw the ramp, unfortunately it was green mana and phage costs 4 black mana so the ramp wouldnt really help you in this regard. should be a lot more reliable with cultivate, rampant growth and the birds now. really nice

you wouldnt use lure on phage. you'd use it on any other creature so that all creatures have to block the other one and phage can go unblocked and thereby win you the game... no need to kill the opponent's creatures first

alternatively you'd at least exchange the llanowar elves with birds of paradise. you definitely need more black mana sources if you want to get out phage before turn 25

how about spore frog instead of Undergrowth (or Darkness)? that way you'd even prevent combat damage if you spent all your mana.
also, even though i'm not really a friend of rituals, this really seems like a deck that could benefit of dark ritual (or more swamps). with only 8 swamps you are not only dependant on drawing phage but also 50% of the swamps in your library! (if you're looking for a cheap dual land may i suggest Tainted Wood?)

did you consider Malfegor instead of Pathrazer of Ulamog? i love this guy, helps you discard, annoys your opponent and is the sweetest combo i've seen so far with It that betrays

for cheap discard:
- Strongarm Tactics (remember you can target creatures in opponent's graveyard with animate dead :) though it works less well with exhume)
- Cabal Therapy (nice bonus: you can use the flashback to save creatures that would otherwise be exiled / returned to your hand etc)
- Thoughtseize