Make room for:
Wandering Fumarole -> replace Mountain

Need:
The Mirari Conjecture
Bonus Round
Unwind
---
Reiterate
Increasing Vengeance
Expropriate
Temporal Fissure
Prophetic Bolt
Izzet Chemister

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Consider:
Unwind
The Mirari Conjecture
Jaya's Immolating Inferno
Rite of Replication
Rewind
Windfall - Cheap refill
More ramp (Fellwar Stone?)
Young Pyromancer - This really should be in the deck
More ways to protect Mizzix (Darksteel Plate, Neurok Stealthsuit)
Mind's Desire
Call to Mind
Sunbird's Invocation
Propaganda - Live a little longer
Rise from the Tides - Another spell based threat
Impulse
Geistblast - Another slot on the curve, plus another copy effect
Thing in the Ice
As Foretold
Blustersquall - Protection for a turn, and also makes Empty the Warrens a better wincon
Steady Progress - Proliferate + cycle
Leyline of Anticipation - Play at instant speed
Brainstorm - Cheap cantrip at instant speed, but I don't really have any way of shuffling besides a few tutors
Worn Powerstone - Ramp
Curious Humonculus - Replacement for Baral
Whispers of the Muse - Reusable cheap card draw
Pore over the Pages
Quiet Speculation
Repeal
Foil - Maybe not enough islands?
Quicken - Allow me to cast a boardwipe at instant speed, probably
Seething Song
Pull From the Deep

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Considered cuts:
Epic Experiment - Probably too many X-cost spells
Fuel for the Cause - I have quite a few other counterspells, but if getting the experience count high enough is hard, this might be worth playing
Fall of the Titans - Basically can't be cast as the only spell in a turn, but it can target to players or creatures at instant speed
Mizzium Mortars - One-sided boardwipe, but 4 damage doesn't kill all the scariest stuff, and RRR is pretty color intensive
Curse of the Swine - Sorcery speed and leaves them with a body for each thing exiled, so it's not great against boards that are scary simply because they are wide
Fanning the Flames - Probably too expensive, but the buyback is good to have on a finisher
Charmbreaker Devils - If I need to cut down on permanents
Sphinx-Bone Wand - One of the least fun of the pay-offs
Swiftfoot Boots - Replace with something that only protects?
Reality Spasm
Inner Fire

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Lands:
Should add:
Shivan Reef
Command Tower
Command Beacon
Spirebluff Canal

Consider:
Highland Lake
Evolving Wilds
Terramorphic Expanse
Vivid lands
Halimar Depths
Cycling lands
Boseiju - Make a finisher uncounterable

Consider cutting:
Mirrorpool - ETBT, no colors, and can only copy once, which requires another colorless land
Arcane Lighthouse - Do I need to get through hexproof?
Desolate Lighthouse - Expensive to activate, and doesn't add color

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Cuts:
Burn From Within - Have enough other X-burn spells, and this is the weakest one. Might be needed if there are too many Ulamogs around
Muddle the Mixture - Would rather want a hard counter, and can only play so many. The transmute does add quite a bit of versatility, but I don't have a lot of relevant spells at CMC 2
Empty the Warrens/Grapeshot - I probably won't have huge storm turns usually, and these are much worse in EDH
Jori En - Can never draw more than one card per turn, and not even guaranteed to do so
Inexorable Tide
Hypersonic Dragon - My sorceries are not that important to play at instant speed
Condescend - Probably have enough counterspells
Swan Song - Enough counters
Steam Augury - Replaced with Fact or Fiction
Red Sun's Zenith - Replaced with Fanning the Flames
Crush of Tentacles
Recurring Insight - Replaced with more cheap draw spells
Time Warp/Time Stretch - Cut down to just one extra turns spell
Niv-Mizzet, the Firemind - Cut down on non-creatures, and at the point where he deals any significant amount, the card draw alone is probably sufficient (plus he's in Mairsil anyway)
Ghost Quarter - I don't have any more copies, and even though having some land hate is important, the deck is color intensive
Temple of the False God - I only play 35ish lands, and this doesn't add any color
Chain Reaction - Boardwipe if the board goes wide, but lousy against a few big creatures
Banefire - Uncounterable, but can only target one player
Wild Ricochet - I don't think there are enough targeted spells that I need to redirect, and this is quite expensive for a Fork
Faithless Looting - Card disadvantage
Reverberate - In most cases, I'd rather just cast another spell than spend RR to copy one
Aetherize - Only works when they're already attacking me, and only works one turn, plus I have to hold up up to 4 mana
Deep Analysis - Sorcery speed 4 mana for just two cards is a bit steep
Beacon of Tomorrows - The deck is probably boring enough to play against as it is
Rhystic Study - I can probably draw enough cards without this, so this is better used in e.g. Mairsil