This is my Niv-Mizzet, the Firemind EDH deck. It is a CASUAL deck intended for multiplayer. It does not have Curiosity or Ophidian Eye on purpose. Do not suggest those cards. The deck is meant to win by drawing cards without infinite combos. It is not built for 1v1, so don't expect to duel successfully with it.
The deck wins by drawing cards. That's it. Could it win by other means? Yes. But it would be an extreeeeeeeeeemely secondary means.
Early game, you'll want to establish your mana base and use some early card draw to set up your overall draw engine and any small combos that can get you to victory.
Your Primary means of victory will be Niv-Mizzet's triggered ability dealing damage when you draw cards. Play Niv-Mizzet when it is advantageous and draw cards as much as possible.
Psychosis Crawler will also get you to victory in the same manner as your general, but can do so even faster since it makes EACH opponent lose life for each card you draw. Still, since this can wipe out multiple opponents at once, you want it as a back up in case your opponents keep the Firemind off the board. They will be gunning for him and there is nothing sweeter than dropping this guy just before you go off after everyone else has thought they shut down Sir Mizz-a-lot.
You can win through attacks, but I have done so only a couple of times and only when it was down to me and one opponent left and their life total was low. The best attackers are Psychosis Crawler and Spellbound Dragon. The Dragon can pull off some surprises. Discarding Enter the Infinite to Spellbound's ability will result in a lot of "Oh, snap!"-style reactions.
The control in this deck is not as strong as some. That is because the deck is built for multiplayer and to be a little more political. The control cards are mostly for defense and interfering in other squabbles to swing momentum in your favor.
Aetherize and Aetherspouts should keep opponents at bay and at the very least hesitant to attack you. No one wants their army in their hand or on top of their library. Propaganda can thwart creature swarms, Chaos Warp can shuffle away a pesky enchantment, and Cyclonic Rift is the powerhouse everyone knows about. Try to use Rift defensively, though. If you use it to protect yourself during a potentially devastating attack, most of the innocent players are going to point at the attacker saying he should have known that would happen and blame him for their set back.
Their are only 6 counterspells in the deck. Your chance of getting one is relatively low, so use them wisely. Yes, the card draw makes the odds better, but treat them as if you did not have that advantage.
There are multiple tutors. Mystical Tutor will net you an important instant or sorcery, as will Firemind's Foresight and Merchant Scroll. Fabricate will fetch you Neurok Stealthsuit, Vedalken Orrery, etc. Tolaria West is just another way to get you Reliquary Tower or any other important land if needed.
Your Planeswalkers are tools, not important parts to the puzzle. Try to make them seem more dangerous than they really are. Get as much value as you can out of them, but if the opponent is aiming for the Planeswalker, they are not aiming for you. Ral Zarek can help get an extra mana early if need be or get rid of a small commander or threat. His ultimate is fun and can be extremely helpful. Chandra Nalaar can help get rid of creatures. Tamiyo can help tap down a troublesome creature and even net you cards after someone's attack. Her ultimate is just too powerful to be allowed to happen for this deck, so expect her to be an immediate target. Jace is as absurd here as he is anywhere else. With Niv-Mizzet out, his repeatable "Brainstorm" can also net you three damage to disperse as you please.
The shear number of cards that can potentially draw you more cards should be able to propel you through the deck.
Important Utility cards
1.) Neurok Stealth Suit - You might have noticed that I do not have Lightning Greaves or Swiftfoot Boots in my deck. That is on purpose. They are inferior cards. Why? Neuork Stealth Suit grants the same level of protection, but at instant speed. What if you play Niv-Mizzet , but the opponent removes him before your Boots' equip resolves? Too bad. No commander for you. But, with the Stealth Suit, you can respond to removal at Instant Speed. With an activation cost of UU, it is like a counterspell for removal. Shroud works perfectly since we do not use Curiosity in the deck.
2.) Venser's Journal - This card grants you life gain while also giving the coveted ability of having no maximum hand size. Feel like gaining over 60 life the upkeep after Enter the Infinite resolves?
3.) Vedalken Orrery - This is one of the most underrated cards in the deck. Playing Omniscience or Niv-Mizzet himself at the end of an opponent's turn is powerful, allowing you to keep your mana open for crucial control and defense cards.
4.) Future Sight - This card can help you dig through your library quickly. Futuresight allows you to play ANY type of card off the top of your deck. Futuresight with Omniscience in play is so good, it's almost stupid. Wait to drop your lands for the turn while this is out so you can play one off the top of your library to get it out of the way and keep digging.
Obvious Combos
1.) Niv-Mizzet + Enter the Infinite: Yes. I do feel like doing obscene damage this turn and having my entire deck in my hand.
2.) Omniscience + Enter the Infinite: If you have Omniscience out and Enter the Infinite resolves, you win unless something horrible on your end or amazing on the opponents end happens.
3.) Laboratory Maniac + Enter the Infinite: If all else fails, go with the final back-up plan. Cast Enter the Infinite with the Maniac on the battlefield and just draw 2 more cards. You win.
Not-so-obvious combos
1.) Enter the Infinite + Spelltwine: I love this combo more than any other in the deck. It catches people off guard. You just discarded Enter the Infinite with Izzet Charm? You must be desperate. Nope. Spelltwine is casting it from my graveyard for a discount.
2.) Omniscience + Mindmoil: Enter the Infinite is somehow thwarted? No matter. Mindmoil is here to save you. Everything you cast is going to draw you a new set of cards equal to the number of cards left in your hand. With all of the card draw in this deck, your hand size can grow or at least remain steady. You'll be able to string a lot of draws together based on available mana. If Omniscience hits with Mindmoil, you can create a semi-infinite loop. GG. Potentially anyway.
3.) Enter the Infinite + Beacon of Tomorrows: I have had so many people tell me I'm crazy for including Beacon of Tomorrows over any other "extra turn" cards. That is, until they find out why I'm not so crazy. If Beacon is the last card in your deck. You now have infinite turns as long as you have the mana to cast it. Draw the Beacon, cast it to get an extra turn and shuffle it into your empty library. Take the extra turn, drawing the Beacon. Play Beacon again and shuffle into empty library. Take extra turn... You get the picture. Enter the Infinite gifts you the ability to have the Beacon as your only card remaining. Time to "goldfish."
Tips
1.) "DRAW, DRAW, DRAW!!!" Remember that the solution to most of your problems is to draw more cards. This deck is riddled with utility and answers. Keep digging until you get to them. It just so happens that its also winning you the game... one damage... errrrrr... card at a time.
2.) "Hurry Up And Wait!!!" This deck is all about being patiently impatient. Draw and keep what you drew in your hand until it's needed. Impatiently draw. Patiently cast. Same principle works with your commander. Wait until you know he will hit the board AND you can protect him. He is the key to the puzzle. You can wait until its the perfect time to add that last piece.
3.) "Don't just deal bits of damage. Deal all of it." This is essentially an expansion of the last point, but is important to distinguish. One of the most entertaining and versatile aspects of this deck is it's ability to go off in one turn. You don't have the stupidly un-creative, Curiosity-style combos, though. What you do have is a multiple, versatile, intricate combos that can win. When one piece goes down, just throw in another. Be patient enough to understand that lurking and lagging while the rest of the table pounds each other into oblivion is to your advantage. Wait to play the last combo piece until the rest of the table is distracted. Then... WHAM. You've sucker-punched them all at the same time. You have that power. Use it wisely.