I'm beginning to like this deck! Using this maindeck and sideboard right now:
2 x
Opt2 x
Shivan Fire2 x
Syncopate4 x
Growth Spiral2 x
Search for Azcanta3 x
Sinister Sabotage2 x
Fiery Cannonade2 x
Rekindling Phoenix4 x
Chemister's Insight4 x
Wilderness Reclamation3 x
Niv-Mizzet, Parun4 x
Expansion//Explosion26 x
landSideboard:
2 x
Negate2 x
Lava Coil2 x
Fiery Cannonade2 x
Thrashing Brontodon2 x
Crushing Canopy2 x
Gift of Paradise1 x
Rekindling Phoenix2 x
Biogenic Oozevs.
Sultai-all Niv-Mizzet, some Expansion//Explosion (depends on how many discard spells they're running), some Fiery Cannonade (depends on their post-board plan: pay attention to whether they keep in Llanowar Elves or bring in Kraul Harpooner)
+Rekindling Phoenix, Biogenic Ooze, potentially Negate
Switch removal around based on what you see. Thief of Sanity is especially dangerous and needs to die immediately. They can have Hostage Taker post-board to answer your creatures, but fortunately Shivan Fire can kill Hostage Taker. If you're running Shock instead of Shivan Fire then things get more complicated; I'd probably hedge towards using Lava Coil instead. If given the choice, use Syncopate on Hydroid Krasis so they can't recur it. Don't expose Wilderness Reclamation to Vivien if possible.
vs.
Esper-Fiery Cannonade, possibly one Growth Spiral, Opt (since games go long and you don't need to cantrip so much)
+Negate, Rekindling Phoenix/Biogenic Ooze depending on what you see, Crushing Canopy
It's going to be a long grind post-board. Don't tap out for a threat if they can play Teferi after; you can't easily get it off the board. If they play Thought Erasure, copy it with Expansion if possible. I'd probably not go for both Phoenix and Ooze because there's not enough space, but one or the other depending on what removal you see. If they keep in Vraska's Contempt, then bring in Ooze; if they have Kaya's Wrath, then use Rekindling Phoenix.
One or two Crushing Canopy makes sense since they kill Thief of Sanity as well as Search for Azcanta. I would board down on Shivan Fire, but not cut htem completely.
vs.
Mono White-Niv-Mizzet, Expansion//Explosion, Sinister Sabotage, some Wilderness Reclamation
+all removal spells, Thrashing Brontodon, Rekindling Phoenix, Biogenic Ooze
Not a good matchup. Hopefully you can stabilize behind the tough-to-remove creatures. Not sure if Gift of Paradise is worth it. Also not sure if 4x Fiery Cannonade is worth it. It's good some of the time, but a single Cannonade often doesn't do enough damage, and casting two is just too mana intensive. On the other hand, if one does not bring in 4x Fiery Cannonade in this matchup, they should go out of the sideboard since they're not relevant enough in other matchups. Brontodon is imperative because it not only blocks well, their answer (if they have an answer) to Phoenix is Conclave Tribunal, and Brontodon kills it.
vs.
Mono Red-Niv-Mizzet, some Expansion//Explosion (this is better vs. MonoR than MonoW because you can copy their burn spells to kill their creatures), some Wilderness Reclamation
+all removal spells, Thrashing Brontodon, Rekindling Phoenix, Gift of Paradise
Same as above. It's important to have the creatures to turn the corner with, because if you both play draw-go they're eventually going to draw the burn to finish you off.
vs.
Mono blue-Expansion//Explosion, Sinister Sabotage (fighting counterwars is a bad idea against a tempo deck)
+all removal spells, Rekindling Phoenix, Crushing Canopy
Not sure about this matchup at all. What do you think? How many Fiery Cannonade would you keep in, would you really bring in all removal spells?
Pre-board Niv-Mizzet outright wins the game, post-board Crushing Canopy can kill Deep Freeze (one of their only ways to beat Niv-Mizzet). Phoenix resolving is big game against them as well.
vs.
Nexus-Shivan Fire, Fiery Cannonade, Rekindling Phoenix
+Negate, Crushing Canopy, Thrashing Brontodon
This assumes they don't transform, which they probably won't, because if they do then just land a Reclamation on the turn they tap out for a creature and you're in good shape. If given the choice, use Syncopate on Nexus.
vs.
Gruul-?? (Search for Azcanta?)
+Rekindling Phoenix, Thrashing Brontodon
No idea about this matchup as well. The main concern from their part is Rekindling Phoenix, which you have no answer for save for countering it, and Cindervines. Brontodon is likely a shoo-in, but Crushing Canopy seems like overreacting since it has no other targets. I am not sure what to board out. Instinctively I'd take out Niv-Mizzet because it dies to Collision/Colossus, but it's one of the only ways you have to permanently kill their Phoenix. Counterspells are probably poor, but they can counter these problem cards. I have no idea. What do you think?