CREATURES
Soulflayer
It obviously wouldn't be a Flayer deck without this guy in it, so an immediate 4 of is included. If the graveyard isn't going your way or you NEED a creature ASAP you can just play it as a 4/4 vanilla creature for 2 black. That scenario shouldn't happen too often as you'll have 21ish other creatures in the deck to trade with/eat removal and fill the graveyard for SoulFlayer.
Birds of Paradise
It's primarily a 3-colour deck and has a few higher cost creatures. Birds helps with mana-fixing and ramp, with the added bonus of giving our Soulflayers Flying. Don't be afraid to chump an attacker with these if you have the mana you need. It'll only make Flayer better.
Sylvan Caryatid
Very likely the best Hexproof option available. Plays a similar role to Birds of Paradise but also has a more useful ability for Flayer to eat, can block weak attackers, and can help your Flayer stay alive if Liliana of the Veil arrives on the field to ruin your day.
Vampire Nighthawk
Flying, Deathtouch and Lifelink for Soulflayer to eat, need I say more? Well, ok, it's a pretty solid creature on it's own and can deter opposing creatures from attacking. You'll almost always want this to eat removal or trade with a creature to put this in the graveyard to be recycled, but otherwise it can hold it's own ok. The lifelink is essential for the Burn matchup.
The one problem with this card? Dies to Lightning Bolt. Paying 3 mana for a card for it to get killed immediately by a 1 mana card can set you behind. But that could also be a mistake for your opponent to give you Flayer-fuel. Let's try to look at the positive things.
Savageborn Hydra
The card that makes Soulflayer very dangerous with Double Strike. I've been tossing up between this card and Viashino Slaughtermaster but this card works well with ramp and is much better late game, able to win the game on it's own if left unchecked. Just remember not to invest too much mana into it if you have other options. If the opponent kills this it's no biggie since you sorta want it dead anyway, but if it can take down a couple of creatures first that's even better.
I will be testing both this and the Slaughtermaster to see which performs better.
Xenagos, God of Revels
In Progress~~~
