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I would cut Desecration Demon. Replace Gild with Ashes to Ashes. A lot of EDH decks run recursion and you're not running mill so Mindcrank is almost a blessing in disguise for your opponents. Leechridden Swamp activates Rakdos. Winding Canyons to flash in Rakdos during an opponent's turn. Cryptborn Horror is cool but situational, you probably want to run something else. Sheoldred, Whispering One to retrieve fatties from your graveyard. Akoum Refuge is slow, maybe replace with Graven Cairns or Blood Crypt.

I added in all your advise, since I find myself aggreing with you. Now I need to cut three final cards. Maybe magmatic-force, gratuitous-violence and archfiend-of-depravity?

I would agree. Mogis, God of Slaughter is also lackluster. You also don't have a way to abuse Wurmcoil Engine (but you may be able to cast it for free).

I'll change it up later, once I have made up my mind. Thank you for your help, much appriciated :)

Anytime amigo.

Let's cut some cards: Artisan of Kozilek. Might as well pay 1 more and cast Kozilek, Butcher of Truth. Magmatic Force provides very little immediate value. He's costly and needs to survive to do much. I'm really iffy on Kaervek the Merciless. I'd swap him to the maybeboard for now. Myr Battlesphere shouldn't be here. You don't have many ways of using Butcher of Malakir here. It's should leave. Inferno Titan is not good enough. Same goes for Scuttling Doom Engine, Xathrid Gorgon, and Staff of Nin. Archfiend of Depravity is terrible. You're Rakdos. Don't give people choices. Besides, the decks with the highest priority creatures usually only tend to run a few on board anyways.

Is your meta very creature heavy? Do people attack you often? If so, Kazuul, Tyrant of the Cliffs is fine. Otherwise it's terrible. Palace Siege is too slow. Gratuitous Violence may be a bit win-more. Gilded Lotus is too heavy as far as ramp is concerned. Be very careful with Underworld Cerberus. Diabolic Revelation is not a very good black tutor. I'd recommend Vampiric Tutor if you can afford it. Pestilence is meh. Same for Pyrohemia. Go with Damnation if you can afford it. Remove Lobber Crew. Maga, Traitor to Mortals is just unwieldy. Might as well run Exsanguinate for that effect. Prodigal Pyromancer and Vulshok Sorcerer are just meh. Chromatic Lantern isn't needed here. Rakdos Keyrune is shit. We'll need to replace them with better ramp. Read the Bones, Sign in Blood, and Toil / Trouble are too bulky in EDH. Rakdos's Return isn't good in a multiplayer format. Tormented Soul and Goblin Fireslinger need to leave. Rakdos Carnarium is the ideal target for land destruction. You don't want someone pointing a Strip Mine at this. If you can afford them, get Blood Crypt, Bloodstained Mire, Shadowblood Ridge, and Sulfurous Springs.

Annnnnd breathe... Ok. I got through that.

I've just spent some time ragging on all the cards in your deck that I don't like. Why? Because Magic is primarily a game about managing resources and you've chosen to play a color combination that's known for not having the best way to collect resources. That means getting the most bang for your buck for the cards you cast is incredibly important. What do I mean by that? Well, instead of playing Butcher of Malakir, you could put in Thundermaw Hellkite. He costs less and there's immediate impact when he hits the field. You're limited to drawing one card and placing one land on the field per turn. Those two things are limitations to what you can do. By actiely looking to break those limits, you'll make a faster deck. Seems self-explanatory, I know.

What you basically want is a smaller curve. Because your commander can make spells cheaper, it's ok to have some higher costing cards. Still, your non-creature spells should be cheap and high-impact. This deck should be between 2.5 and 3.5 average converted mana cost. To help you cast spells, you need proper ramp. The fact that you don't even have a Sol Ring speaks volumes. I highly recommend Braid of Fire and Talisman of Indulgence. They're two cheap rocks. Charcoal Diamond is a decent rock, as is Jet Medallion since your primary color is black. There's also Mana Crypt, but that's serious money.

That's all I have time for at the moment. Hope that helps.

Now I have made alot of changes removing many cards I agree were kinda pointless in the deck to begin with. Some are still there espicially the pingers, reason being that I want easy acess to Rakdos as soon as possible. If I have any of these out the turn prior to Rakdos, I can play him by simply tapping one of these resources and begin cheating out big guys. I really liked the artifacet suggetestions you made tho, made the deck that much more consistent, and also the lands I forgot about. Some others are going when I have time to replace them.

Ty for the help TheDevicer, much appriciated :D

Other cards that could help with colourless mana is Mana Vault, Basalt Monolith and the more expensive Grim Monolith. A land you could consider is Phyrexian Tower :D

Going to give you a few more cards to consider, not sure if they would fit the theme but many of them are worth(?) considering :D

Creatures

Knollspine Dragon: Can help you refill your hand after dealing some hefty damage, ideal scenario could be swinging for 6, discard 2 cards in your hand and draw 6 new.

Anger: Haste enabler if you have in the graveyard, could be useful paired with Entomb or simillar effects.

Maga, Traitor to Mortals: Mana sink late game/ win con for good damage or easy enabler to cast Rakdos. and Mikaeus, the Unhallowed is also creatures you can consider.

Instants

Bituminous Blast: 4 damage to face or to kill a creature and it has cascade.Cauldron Dance: Reuse ETB effects from creatures, surpise attackers or blockers.

Sorceries

Decree of Pain: A board wipe that draws you cards for each creature.. or cycle it, your choice.

Exsanguinate: With excess mana, this spell can be a win con. by itself.

Fumarole: A bit costly but gets rid of a pesky troubling land, that Maze of Ith stopping you? Gone. Also killing a creature is a bonus.

Torrent of Souls:Reanimate spell with the added bonus of giving your returned and other creatures haste and +2/+0, useful for that last bit of damage to end the game or kill some creatures.

Buried Alive: Unlike Entomb, this card let's you put 3 creatures in the yard to reanimate later.

Mind Twist: Useful with excess mana to make a player discard their hand, perhaps putting something tasty for you to reanimate in their yard.

Enchantments

Animate Dead: Continueing the reanimator theme, this could be handy.

Necromancy: Another reanimator spell that can be cast as it had flash.

Dance of the Dead: A worse Necromancy or Animate Dead, more is better I say.

Sneak Attack: Quite pricy enchantment, but this wonderboy allows you to get out creatures for cheap for a world of hurt. If you run reanimator you can get them back onto the battlefield for cheap.

Stranglehold: No extra turns for the pesky blue players.. also no tutoring.

Waste Not: Works well with discard spells, potential mana, zombie tokens and card draw in one package for 2.

Artifacts

Expedition Map: Let's you find the Urborg + coffers combo more easily.

Sensei's Divining Top: Top deck manipulation is always nice.

Coalition Relic: Mana fixing or "ramp".

And a planeswalker I recommend is Liliana Vess.