I am wondering if you can come up with a powerful B/G deck that  is supported by my partners Blue counter deck.

 

my deck currently runs off

creature 23
4 Mortivore
4 Revenant
1 myojin of nights reach
4 dauthi horror
3 ogre marauder
4 nether shadow
1 netherborn phalanx
1 scion of the wild
1 kokusho the evening star

 

spells23
4 dark ritual
4 rancor
4 moldervine cloaks
2 lightning greaves
2 hex
3 soul burn
4 golgari signet

 

land 15
3 vault of whispers
4 golagri rot farm
8 swamps
4 forest

 

I want to keep the
mortivores, revenants,  and rancor's anything else can be changed

 

my budget is $ 80

You want to keep the Mortivores, Revenants, and Rancors, eh?  That sounds good: Rancor is an awesome card, Mortivore has a lot of power, and Revenant is essentially a Flying Mortivore, which is even better.  I take it then that the strategy of this deck is to fill the graveyard with creatures, and use your Lhurgoyfs.... Lhurgoyves..... Lhurgoyfi..... to present ever-worsening threats while your teammate keeps all your opponent's relevant spells at bay.  Sounds like an excellent plan.
 

Of course, even with that bringing down your mana curve, it may not be enough.  You've got a 61-card deck, with 15 land, 4 Golgari Signets, and 4 Dark Rituals.  Your most expensive card is now Hex or Kokusho, and your most important cards all cost either 4 or 5.  That's just too much pressure to draw enough land, especially in a deck with no ways to draw extra cards.  I think the best option is to drop Hex (I know I said I wouldn't, but something's gotta give) and replace it with one copy of Svogthos, the Restless Tomb.  That brings the card count to 16 land in a 60-card deck, which is better but still rather risky.  Of course now you only have one 6-mana card (and it's Kokusho, which is awesome enough to justify it), and your Signets and Rituals, so hopefully you'll be alright.