TheBear

I've... Got no clue actually, nothing else is banned. Unless there is like some weird card pairing that's not allowed.

Take out all 4 and put in 4 extra islands.

I would check out Primordial Hydra, things a killing machine. And then maybe a Doubling Season or two, so the counters you put on your hydras pile up much more.

Found it, Tolarian Academy is banned, and is only limited in Vintage.

Well, other then adding in Shock lands and maybe a Terramorphic Expanse, I think you're all good sir.

I would still put in Slaughter Party, it can break combo decks, which can guarantee a win.

Well, Fallout can't be countered as well, so maybe still run like 2 in the sideboard, incase countering is going on alot.
Or even Damnation could have a spot here, just downright blow everything up.

Well, maybe think about putting in like Slaughter Party (I believe that's the name) Maybe cards like Volcanic Fallout to help give this deck ways to deal with token decks and hexproofs. A Pith needle or two.

Unless you stick Laboratory Maniac into the deck, so decking yourself out could end up being a win condition. And for the Mizzet, I can see him being good, allows you to deal even more damage by drawing, and gives a body to assist with blocking. But, I just thought of a card. If people are drawing a shit ton, and are possibly being forced to discard. Why not having cards that deal damage when players discard also? Can't remember the name but it's Liliana's something.

Look's pretty solid to me, if you want to keep the Cacklers, a nice card to pair them with is Lyzolda, she turns them pretty much into miniature Hellhole Flailers that also draw you a card when you sac them. I see where people think Rakdos would work in this, but his ability to cheapen your creatures won't entirely work, as it removes generic. So the most it'll do it make Hellhole 1 mana cheaper, still a 6/6 flying trample is nice, but you got the Demigods to kill players.
Also, have you thought about anything for the side board?

And just noticed, but Jin-Gitaxis, Core Auger could work for this deck also.

Well, first which Mizzet, Rtr or original? Then for the Command, maybe Trade Secrets, yes it works for your deck, but I can see it backfiring possibly.

I would look maybe into adding in Gift of Orzhova, it's a very powerful enchantment that also gives in 2 for white devotion, and even 2 for Black devotion incase it's required.

The three mana is true, can be painful. But you do have Jeleva, so the opportunity of it being free is there, and it does have 3 other abilities instead of just countering.

Oh, well. Fail on my side, I was looking in the Artifact Creature, that's why I couldn't see him xD.
But in other things, other cards of use could be Minds Aglow, Arcanis The Omnipotent, any of the Jaces if you can get your hands on them. Preferably the Jace that causes a player to draw 20 cards. Cryptic Command would work nicely, a bit pricy, but for good reason.

I would maybe think of adding Psychosis Crawler, as you draw cards you are dealing more pain out to everyone.

I see. Well, I still stand by the Dredge idea. But hey, your deck so your choice lol.

Then possibly add in cards to reanimate creatures? You are playing black after all, staple for most reanimating.

If you want a VERY good way to fill the graveyard, use the Dredge mechanic. Things such a broken mechanic that it's used in Legacy, and it's in the Golgari colors.

You got 2 Niv-Mizzets. Otherwise it looks pretty good.