Mono-Red Burn is easily the least expensive deck to play in Modern that has any chance of winning. But Mono-Green Infect can definitely hold its own. There are more other budget variants, such as Mono-Black Infect, which is more of a control-oriented build. Then there's a deck on opposite side of the financial spectrum with BUG Infect, which is more consistent, but requires quite an investment in the mana base.
For today’s list, we’ll base it off of a list run by Wigi in a MTGO Modern Premier. He piloted the deck to a 4-1 finish, but that was back in 2014. To update this list to include newer cards, there are some major adjustments made to the list. Let’s take a look.
4 Glistener Elf
4 Ichorclaw Myr
4 Apostle’s Blessing
4 Vines of Vastwood
4 Mutagenic Growth
4 Blossoming Defense
2 Become Immense
4 Cathedral of War
The deck plays only 12 creatures, all of which have infect. Let’s break them down.
Now onto the non-creature spells. There is actually one non-Green card in the deck.
What’s so useful about this card is that it gives a creature (or artifact) protection from a color of your choice or artifacts until end of turn. The artifact part is especially useful when facing decks that utilize artifact creatures like Solemn Simulacrum and Wurmcoil Engine, both of which are seen quite often in Modern. That protection can give one of your Infect creatures the chance to strike for lethal, an effect well worth paying 2 life for. That’s why there are 4 copies of it in this deck.
Gaining that extra two power and trample allows you to be far more aggressive in attacking, especially when knowing you’ll get Rancor back if and when that creature dies in combat or is removed from the field. Multiple copies of Rancor on a creature can spell the end of the game for your opponent.
I should note that the effect to return it to your hand only works if it actually makes it onto the battlefield. Were you to try to equip it to a creature and that creature is destroyed before the Enchantment resolves, it will simply go to the graveyard and it won’t come back.
There are the full four copies of it in this deck, taking the place of 2 Ranger's Guile and 2 copies of Might of Old Krosa.
For a single Green mana, it gives a target creature +2/+2 until end of turn. However, if you play it during your main phase, and not as a combat trick, that creature gets +4/+4 until end of turn instead. Because it’s not as useful as a combat trick, there are only 2 copies of it in the deck. It’s a very solid card nonetheless.
But Khans of Tarkir gave us Become Immense. While on the surface it costs 6 mana to cast, it has Delve, which allows you to remove cards from your graveyard to make it cheaper. The +6/+6 can win you a game out of nowhere. As just another +3/+3 pump spell, Giant Growth is now redundant.
Now we take a look at the lands. We start with 12 basic Forests. Then we have an interesting card called Cathedral of War.
As there are four copies of Cathedral of War in this deck, that’s a potential additional +4/+4 as long as you have a creature attacking alone, which oftentimes with this deck is not all that unusual. The one downside to this card is that it enters the battlefield tapped, but in a deck like this with such a low mana curve, that’s not a huge drawback.
For the sideboard, we have 4 Tormod’s Crypt, a zero-drop that can tap to remove all cards from a target player’s graveyard. This can deal with any graveyard strategies, and hurt opposing Tarmogoyfs by depriving them of card types in the graveyard. There are 4 copies of Nature’s Claim, which is a one-drop Green instant that destroys a target artifact or enchantment, but gives that player 4 life. Then again, life totals do not matter when you are playing an Infect deck.
There are 2 copies of Fog in the sideboard, to help protect you from aggressive strategies that simply have more creatures than you can handle. By playing Fog when an opponent is swinging out, you get to prevent all combat damage. There are also two more copies of Might of Old Krosa, and an additional copy of Ranger’s Guile.
The problem is that the cost of four Nexus doubles the cost of the entire deck. A playset of Nexus can cost about $100 (as of December 2016). It's because Inkmoth Nexus also sees a lot of play in Modern Affinity decks that can equip it with a card like Cranial Plating for a quick finish. If you do want to pick up a playset of Inkmoth Nexus, it is well worth the investment.
Also, I’d like to point out that the New Phyrexia Event Deck: Rot from Within has quite a few of the cards you’ll be needing for this deck, including a ton of the pump spells.
If you’re looking for another Modern deck for you that you can build on the cheap, let us know what sort archetypes you would like to see reviewed.