Enjoy the concept of the deck, what about AEtherling over the Codex Shredder or Desecration Demon ?

I have considered Aetherling. It's undeniable one of the top bombs for control decks. It would most likely fit where Niv-Mizzet is at the moment. As a top of the curve finisher. The Desecration Demon is a newer addition I've done and it's very valuable as a possible early game threat and way to just apply pressure. Codex Shredder was an experiment 1-of a few months back that has just blown me away with how awesome it is. It feels so good to see they're Obzedat hit the GY without being a dedicated mill strategy and I am not afraid to cast an 8 mana counterflux in the late game, or get my niv-mizzet back. I could also drop the 2 planeswalkers for Aetherlings, really like them, though.

Ok first of all, I really like your List,... +1 from my Side
Now what I think about improvements:

Whip of Erebos seems to be out of place in a Deck with only 4 creatures
I reckon you should replace Codex Shredder with Ashiok, Nightmare Weaver , that whould make your Whip of Erebos more reasonable as well,now that I think about that

You should run 2 Steam Augury to bridge your Carddraw till youre able to cast Opportunity
I dont think Quicken is too awesome, so You might want to go down to 2 or 3
And Youre missing Thoughtseize which is such a Powefull Option to have access to.

Turn / Burn should be Far / Away or other more reliable removal such as Hero's Downfall
and finally, but that is personal preference Niv-Mizzet, Dracogenius should be AEtherling
Either way, thats just what I think, let me know If you agree or dissagree, and how stuff works out for you, because this is actually what Ill be running in a very short time from now on, so Im highly intrested
Cheers

This is what I came up with after studying your List, let me know what you think

http://tappedout.net/mtg-decks/grixis-walkers-control/

One of the big problems this deck has is with life. Against red based aggro decks even if I stabilize, I may do so low enough that any top deck burn will kill me. That was the reason for the Whip of Erebos . Also I keep dreaming of Niv-Mizzet, Dracogenius with lifelink so I can have r/b: deal 1 dmg, draw 1 card, gain 1 life everyturn, but I know that is a christmas land scenario.

Codex Shredder is an underevaluated power house. I've thought about Ashiok, Nightmare Weaver and may go that route, but it does change the direction of the deck and I feel I would need to rearrange other things for it. Still something I'm considering.

I agree with Steam Augury . The jump between 1 drop draw and 6 drop draw is very big and I can stumble around 4-6 lands sometimes. Turn and Far are interchangeable, which is why I have the Far in the side board. I opt to MB Turn because it has the advantage of just shooting the player if that option comes up. Hero's Downfall may go in at some point. I like Dreadbore because it's easier to cast. But I am not against swapping it out for the downfall.

If I get to the point where it's a keep Niv-Mizzet, Dracogenius or lose $5,000 scenario, I'll probably go AEtherling . Right now I'm not at that point and the dracogenius is a decent enough bomb. Usually a similar clock, just not as self defending.

Duress will probably be replaced with Thoughtseize .

I could possibly shift a bit toward Midrange for a couple of Gray Merchant of Asphodel . That would also give more creatures for the whip to utilize.

I agree with or understand your decisions
Have a look on my Profile for the Grixis Walker Deck I made after studying yours since links dont seem to work,

There is also a intresting Mono Black Control list you might Consider if you like Playing with Gray Merchant of Asphodel
Im happy to get any Feedbacks, to improve either one

Cheers Mate

okay... totally expected Lazav, Dimir Mastermind as he looks like Emperor Palpatine, the head sith... you made me sad haha

Honestly, I've considered him a lot. With that new revelation I might just have to do it. Sorry to let you down, though.

Id side out 2 angers in replace of Hero's Downfall

Any reason why?

Anger of the Gods fills a different role from Hero's Downfall in that it fights early aggression. Dreadbore fills my kill a creature or planeswalker role and I like the RB cost better than 1BB even as a sorcery.

You should find a way to add in Far / Away . It's one of the great Grixis creature control cards, helping get rid of Hexproofs and Indestructibles.

You could remove -1 Inspiration , -1 Opportunity , and -1 Mountain (I feel like you have too much red mana) to add in +3 Far / Away .

As a fellow Grixis player, I have some questions--what do you bring Izzet Staticaster in against?

And does mainboarding Ratchet Bomb pay off or do you feel like it's a dead card most of the time?

Far / Away goes in and out depending on what I feel is necessary. It fights a more specific range of decks than the other removal I currently have and I've found more recently that draw is better for me. I could go remove an Inspiration and Opportunity for +2 Far / Away if green/white aggro starts to pick up again. My mana is fairly set right now. I won't go down to 24 and I want high chances of red mana for turn 3 Anger of the Gods .

I bring in Izzet Staticaster against the aggresive decks that show a few x/1s (barely boros and rakdos aggro) and against Elspeth / Assemble the Legion .

Ratchet Bomb is my only way to destroy enchantments. I put it side board for a bit and almost immediately wanted it back in the main. Against Aggro it kills cheap creatures as another wipe effect, against mono-black it can kill Pack Rat or Underworld Connections , against control it kills Detention Sphere s.