Alright, this is a big question in some peoples' mind and I have this space to hopefully answer that question.
Why no Valakut?
Red: color of fire and speed. What do I want to do with this deck? Win off of a combo. So, I need to focus all of my attention on that combo and what my opponent is doing to stop it. The counter arguments are that red is a good control with burn and draw mechanics in U/R. Whether or not this is valid, I decided not to take the huge dip in my wallet for another 8 shock lands and have to work even harder on trimming this deck down. Now onto the deck.
I'm going to start with win cons then moving to how they win. First up: Avenger of Zendikar.
He creates an army of tokens that can grow to even 12 power. He is a monster with Scapeshift and I feel like everyone can agree. The only downside is his cost, but in control, cost is nothing. After getting so many tokens, the next best thing to do is to attack right? Well, blockers are no issue with Cyclonic Rift. If I'm playing control, then the 7 mana it took to cast Avenger with counterspell mana left over is enough to cast Cyclonic with counterspell mana left over.
Now #2: Hedron Crab.
While 3 cards per land doesn't seem like much, its a turn one card guys. That means all the other mana accelerants boost this card's potential by a lot. I honestly win more by mill because of the turn one, island crab, turn two, fetch with counterspell, and it just gets worse for them.
Enablers: Courser of Kruphix,
Kiora, the Crashing Wave
, and even Sakura-Tribe Elder are huge ways of getting lands out quick. The more ways that land can enter the battlefield, the better.
Keeping myself alive: Remand, Mana Leak, Simic Charm, Cryptic Command, Cyclonic Rift. Basically counterspells, but with simic charm, giving all, even lands, permanents hexproof is amazing. The last card mainboard that doesn't belong is Serum Visions because it's just a filter.
Sideboard(and matchups): Tormod's Crypt for obvious reasons. Repeal is a cantrip that helps in the aggro with onedrops and works really well with another SB, Beast Within. Beast helps out vs a Blood Moon. Krosan Grip also helps, but it's mainly there for the split second. Split second stops the loop of Splinter Twin and Deceiver Exarch. Lotus Cobra is just there for when my opponent doesn't care about me. When I can take a break from intense control, I want to combo faster. Lastly, Mirror Mockery is just a good card in general. On my creatures, it's amazing, on their's, it's hilarious. A turn two Primeval Titan meets my turn two Primeval Titan. Because screw Amulet Bloom. Some difficult match ups would be affinity and burn because when they dump their hand, it's just no use, they win game 1 most of the time. Also, other control decks are hard because without having to build around a combo, they are typically better positioned.