Creatures
Death's Shadow
The deck completely revolves around this guy. Without him winning is virtually impossible. Usually a 10/10 for 1 mana, he's cornerstone of either a beatdown plan or our combo. PROTECT THIS CARD AT ALL COSTS because if he dies it's probably game over.
Avatar of Hope
You will never cast this card for 8. It costs WW in this deck. Avatar helps us against one of our nightmare matchups; aggro, and even then it may only hold them off for a turn if they've been allowed to swarm the board too much. It also buys us an extra turn against Splinter Twin. Avatar of hope is often a great target for Faith's Shield after a mass block but sometimes you might be better off holding that protection for your Death's Shadow.
Spellskite
Having Skite in the mainboard might seem strange but it does so much work keeping the heat off Death's Shadow and preventing you from getting bolted while on low life. It also has the perk of making Infect, Bogles, Burn and Twin players scratch their head when they see this game one and not know what to do. It's also a solid blocker against some aggro decks like Zoo and can buy you some time. Skite can also be used to drop your life low by repeatedly using its ability on the stack if a legal target is played. There is a singleton Watery Grave that can fetched should you need to use a blue mana for Spellskite's ability later on, just make sure you fetch it before it gets exiled with Plunge into Darkness or Spoils of the Vault!
Removal and Disruption
Thoughtseize & Inquisition of Kozilek
Used early to disrupt your opponents plans and also very useful for holding until you're ready to play your Death's Shadow to extract any removal or counters they may be holding on to.
Path to Exile & Slaughter Pact
Used to clear the board of any threats to buy time for when your combo is ready. Slaughter Pact is a great card for baiting an opponent into thinking you're out of mana.
Protection
Faith's Shield
Looks pretty basic at a glance, but in this deck it's incredibly useful. You can protect your Death's Shadow from removal, keep an Avatar of Hope alive after blocking large amounts of creatures, get your Death's Shadow through blockers to deal damage and use it to protect yourself from a lethal Lightning Bolt in a pinch using it's Fateful Hour ability.
Leyline of Sanctity
Yep, 3 mainboard. Why? Because we are often just one Lightning Bolt away from losing a game. Having this card mainboard has some very good upside benefits though: it makes some extremely good game 1 matchups vs decks that may not be able to remove it until sideboard like Burn, 8-Rack, Scapeshift, Storm etc.
Angel's Grace
This card is a big part of your main combo, allowing you to stay alive until the end of the turn while you go into negative life to deal lethal damage. You CAN also use it as a last resort protection spell (well, you'll usually have no choice) but it hurts quite a bit when you have to use it to stop something from killing you as it stops you from being able to use it for comboing. Also a big part of the reason this deck hoses all-in 1-hit combo decks.
Another little trick you can use is to cast this the upkeep after using Slaughter Pact to avoid having to pay the full cost. Even better if you're ready to combo off that turn.
Searching and combo pieces
Plunge into Darkness
You'll almost always want one of these in your starting hand. It puts you on whatever life you wish while digging through your deck for the rest of your combo pieces. If you have 2 in hand though, you might want to pay less life so you can instead dig twice. It's a terrible late game top-deck though as you'll usually be too low to cast it.
Spoils of the Vault
Here we are, the card that allows our Death's Shadow to hit for 50-60. Throw down an Angel's Grace and name whatever card not in your deck, your entire deck gets exiled, you go to about negative 40-50 life and your Shadow becomes huge. The best part is this can be done at instant speed if your opponent allows a Death's Shadow to get through unblocked.
Alternatively you can name Rite of Consumption if you like gambling and you'll lose life until you hit it. Take very careful notice of how many are still left in the deck though as you may have already exiled them both with Plunge into Darkness. If only 1 is exiled you've got an even better chance of losing enough life to cast Rite of Consumption for lethal. If you don't lose enough life though...well, it's game over for you probably.
Rite of Consumption
See description: Spoils of the Vault
Lands
This deck has some issues with mana. Most spells cost only 1 or 2, so you only want to run a small amount of lands so you don't flood, but to cast your full combo of direct damage at once it costs 5 mana Death's Shadow, Angel's Grace, Spoils of the Vault, Rite of Consumption so sometimes you want to draw mana.
This exacerbates the biggest issue this deck has of not having all the right cards at the right time and just imploding on itself. On top of that, the 5 mana combo costs 2 black, 2 white and 1 colourless, so you'd better hope you have all the right colours.
Marsh Flats
It's no surprise we're running fetch lands in a modern deck. We need as many of the right coloured mana as we can get. A neat little trick you can use is fetching into a Godless Shrine in response to a Lightning Bolt or Dismember to suddenly have a big enough Death's Shadow to survive it and waste an opponent's removal if they're not paying attention. This can also be done after blocks have been assigned to suddenly be big enough to beat that Tarmogoyf.
Cavern of Souls
Sadly, control is a pretty terrible matchup for us. It won't stop them from countering our instants and sorceries, but you can name 'Avatar' as the creature type to allow both Death's Shadow and Avatar of Hope to slip through the counterspells and resolve.
