First is the explanation of All In Red. For those of you who are not as familiar with this term; in Poker, when the player shoves all of his or her chips toward the middle of the Poker table, this action is known as All-In. When we play bunch of Rituals to accelerate into a big beater, we pretty much invest 2~3 cards into the one and only threat on the table, and we hope it will get us to the promise land, which is the victory. Hence, people have named the previous version of deck as All-In and primarily with Red cards, also known as All-In-Red while some might argue it's stompy.
Keep in mind, last time when this deck showed up in any Grand Prix or Pro Tour, the deck did not have weapons in the form of Cavern of Souls
or Goblin Electromancer
. Thank to our beaters being Spirit, they all fully enjoy the advantage of running such land. Even though Seething Song has been banned in Modern, with Electromancer in play, all the Rituals are effectively as good as the good old Song.
Now, to make up for the blatantly obvious weakness of this deck, or to combat Path to Exile, we definitely need all Four Chalices of the Void. To further protect our beaters, main-deck Blood moon can cripple your opponent, depending on the match-ups. The follow-up question is most likely: doesn’t Chalice at 1 defeat the purpose of Serum Vision? Well, Serum Vision is most useful turn 1 while Chalice can be the play after Vision. A Mid or Late game vision with a resolved Chalice at 1 on board usually does not make a difference; in other words, the game has pretty much been decided long before you draw that dead Vision.
Do not for a second considering swapping out Magma Jet, this card serves many purposes in the deck. It smoothes out the draw early game, scrying for either the beater or ritual you need, and providing that extra damage for your need to edge out. Also one caution is the lack of synergy between Electromancer and Cavern of Souls. Sometimes when you have Cavern in your opening hand, you wish it could be a Fetchland or a Steam Vent, so you can produce the Blue mana to drop your Electromancer. Hence in my build, I feel it’s more important to produce the Blue to play Serum Vision and Electromancer than to simply drop the Cavern and say go.
is to improve the consistency of Five Converted Mana Cost beaters and sometimes having a 10/10 or 9/8 lifelink Vigilance beater can just win you the game outright. Now, the split currently is 2 Deus and 2 Empty the Warren. Deus is great in that it works with Cavern, but it is slow and often falls to being the victim of blockers; on the other hands, a resolved Empty the Warren often generates enough Goblins to pass through 1-for-1 creature removal, but it is a horrible card when you have spent Rituals on other things already, hence not a feasible follow-up option. Feel free to experiment the split, could try 3-1 either way, depending on the meta.
Onto the Sideboard choices, Needle is always good against various Planeswalkers from Liliana to Karn or against annoying artifact such as the Birthing Pod. Plaxmanta is great against decks that tend to mess around with your beater. Shattering Spree and Echoing Truth are meant for problematic artifacts and enchantments. Last but not the least, Magus to hose more of these Tron or Scapeshift decks. I might consider Leyline of Singularity to fight against White Tokens deck, or Sulfur Elemental against these White Life-gaining deck, but they aren't really on the radar right now, maybe meta-game will change, who knows.
The key to the success of this deck overall is not to overly analyze or second-guess. If you think too hard, you tend to play less aggressively, which could lead to a squandered opportunity. There is always a calculated risk when you play a deck like AIR, enjoy the solid simplicity of Mana base and have fun.