Messing around with Dragon decks, and I'm a huge fan of Niv-Mizzet. So, I thought I'd make a more-or-less Gimmicky deck based on both versions of him, having cards in the deck for either of him to Infinite Combo someone's Health down to 0 (assuming the amount of cards in your deck holds up).
Here are your Main Combos, the ones you'll be using to win the game outright :) -
Curiosity + Niv-Mizzet, the Firemind
or Niv-Mizzet, the Firemind + Ophidian Eye
- pretty simple here: attach whichever Aura you have to Niv-Mizzet, use his Tap ability, and you will begin a cycle of Drawing and dealing 1 Damage that you can continue until you run out of your deck, or end at any time by not Targeting a Player with Niv-Mizzet's Damage.
OR
Izzet Boilerworks
+
Mind Over Matter
+
Niv-Mizzet, Dracogenius
- this one requires a little more explanation, but is pretty simple as well. First Tap the Boilerworks for UR to use Niv-Mizzet's ability, then Discard whatever card you Draw (it won't matter anyways - you're about to win the game!) to Untap the Boilerworks with Mind Over Matter's ability. Then repeat for as long as you want or until your opponents are dead or you are out of cards.
The rest of the cards in the deck are primarily either to ensure you do not get utterly obliterated before you can start your combo, or to help you ensure you get the needed cards in your hand. Archmage Ascension lets you pick exactly what you want, it'll just need a little help to get into that position - having either version of Niv-Mizzet will easily get you your Quest Counters. Parallel Thoughts won't do quite as well as a Countered-up Ascension, but it will give you a very good chance of getting what you want within a few turns anyways and requires no setup. Invoke the Firemind can give you some flat-out, brute Drawing power if you just can't seem to find your others, or act as an overpriced Blaze in a pinch (plus, how can you not use it when you have the Firemind himself in your deck?). Time Reversal more or less gives you a reset on your Infinite Combos, making it valuable against mass-Healing decks or in long Multiplayer games. Gratuitous Violence is simply there for convenience, doubling your Damage and therefore halving the amount of cards needed from your deck to pull off these combos. The combos themselves are not at all made or broken by having/not having it. Your Phantasmal Dragons and various low-cost Walls are in there just to keep you alive long enough to find all the cards you need, basically. The Dragons do have some stopping power, though, and if everything else was going wrong you may be able to bludgeon your opponents with them. :)
The Maybeboard cards could all be viable in various different situations, with the three card-Drawers being able to replace Invoke the Firemind and the Slumbering Dragon able to replace any of your low-cost Walls. While the Draw options here are not necessarily as versatile as Invoke, they are all cheaper. And while the Dragon forces you to be assaulted before it's useful, an 8/8+ with Flying for R is nothing to sneeze at (and the threat of that monster may be enough to deter attacks in itself!).
Feedback is welcome, I'd be happy to hear any experience you personally have with using the deck, and if you see any (potential) crucial omissions feel free to post them!
