This past weekend I piloted Izzet Phoenix to back-to-back high finishes, including a Top 8 in the ManaTraders event and a win in the Magic Online Pioneer Showcase Challenge. I took the original list from Edgar Magalhães (@EdgarMTG) and made some small adjustments along the way. Here is what I'd currently recommend trying as well as my explanations for all the card choices. Enjoy!

Cantrips

It felt awkward not seeing Pieces of the Puzzle in my opening hands, as it felt like the most efficient way to use three mana to advance my position and I just wasn’t making the most of my turns without it, so I suggest trying four. It is also really good at helping you recover from mulligans and overpowering Go Blank, and it's especially nice to have more as Go Blank decks play Thoughtseize.

Only two Chart a Courses will make it a bit harder to discard Phoenix vs control and combo decks, but I think it’s worth trying this to be able to fit everything else in.

I wanted to fit in an extra Fiery Impulse. With four Pieces of the Puzzle and Expressive Iteration, I felt the deck had access to a lot of card draw, so I've cut a Treasure Cruise for now. That said, Cruise is one of the best cards to find off Pieces, letting you have explosive turns in the midgame, so I am not sure yet.

Burn Spells

I am keeping the main deck Sweltering Suns, as it seems convenient to have access to a board wipe. It's worth noting that if you cut it you can play Jegantha, The Wellspring in game one at least.

I put in a third Fiery Impulse as it felt pretty important to have early interaction. What pushed me to try the third was that I found Lightning Axe somewhat awkward versus BR Arcanist, so I wanted the ability to potentially trim Axe against them post-board. I felt an extra Fiery Impulse would go a long way in letting me do that. I would also expect people to try and fight Phoenix with Burn, though I think in the end Phoenix should emerge victoriously. I played the matchup like six times last weekend and won every time, feeling pretty comfortable along the way. All the upgrades to the deck have made the matchup feel pretty good so far.

The Sideboard

Alternative Threats

The best alternate win-condition I know of. You are pretty good at drawing your deck but can have trouble converting that into winning the game. If you haven’t played Jace before, you will likely be impressed, running away with games by casting this after your opponent Go Blanks you, weaving victorious against Niv-Mizzet Reborn where they have Slaughter Games’d your Arclight Phoenix. The +1 is better than it looks, as milling two can combine with Aether Gust to permanently deal with a threat, in addition to just fueling Cruises and digging to Arclights and Eternal Scourge.

With Pieces of the Puzzle, there is some concern of running out of cards as you rip through your deck, Scourge being a sticky threat you can mill over is quite convenient. I wasn’t too excited about this at first, as investing three mana into a vanilla 3/3 didn’t seem like that good of a deal to me. Even with what it can accomplish vs Go Blank, it represents some virtual card disadvantage because you aren’t leveraging your mana as effectively as possible. It has seemed good enough for me so far.

Counterspells

This card is busted. The second coming of Pyroblast. Three has felt like a pretty healthy number. It could be more, but then you run a higher risk of having awkward spots in the mid to late game where it’s dead. I would say play as many as your gut tells you to play.

This card was brought to my attention by Tristan Wylde-LaRue. The ability to be a hard counter for one mana is quite nice. The Jeskai Ascendancy and Lotus Field decks can produce a lot of mana, and it can be difficult to counter Treasure Cruise with Dispute in the mirror. Negate is a nice card, but leaving up two mana is difficult. To make matters worse, passing to an opponent with a Negate up and having them Mystical Dispute your Negate can be a devastatingly bad exchange that will make you question your entire approach to the matchup. I like trying one Surgery for now. 

Three might seem excessive, but I have been impressed. There are many threatening, difficult-to-deal-with threats like Surrak Dragonclaw and Klothys, God of Destiny. I also got paired into the Mono-Green Devotion deck three times last weekend, and being able to toss around a gigantic Voracious Hydra was nice. You generally want to be able to find multiple of these in a game, so that is why three is a reasonable number in my view.

Removal Spells

A couple more sweepers for when you want them. If you think you don’t want sweepers you can cut them, but having a few seems reasonable to me.

This card is mostly for the mirror, I felt low on answers to Thing in the Ice. Even more so when my opponent had cards like Crackling Drake and my removal felt pretty taxed. Obviously fine to side in other matchups too, but that is the primary reason. Having four main felt a bit much to me, but it’s obviously somewhat marginal stuff.

I wanted a card to deal with creatures that were too large to remove, or indestructible. For example, an Ensoul Artifact plus Darksteel Citadel, or an Ethereal Armored weenie. It brings nice synergy being a sorcery for Pieces of the Puzzle compared to Brazen Borrower, for example.

Closing Thoughts

As a closing note, I will add, the mana base isn't set in stone so feel free to make some changes, it seems reasonable to me, and I don't want to change anything yet or sweat over this small stuff.