I have won by turn 4 with this deck.
Key combos:Heartless Summoning
+
Myr Retriever
+ Falkenrath Noble, Pawn of Ulamog or Bitter OrdealKrark-Clan Ironworks
+
Myr Retriever
+ Falkenrath Noble, Disciple of the Vault, Pawn of Ulamog, or Bitter Ordeal Beseech the Queen or Diabolic Tutor to get Myr Retriever
The combo:Goal is to use a sac method like Krark-Clan Ironworks, Heartless Summoning or Arcbound Ravager to generate a loop of the Myr Retrievers to and from the battlefield to the graveyard to my hand. This mill is infinite once you reduce the MR mana cost by 2 with Heartless Summoning or gaining 2 extra mana with Krark-Clan Ironworks. You can also sacrifice the 0/1 Eldrazi tokens generated by Pawn of Ulamog's ability for 1 colorless mana each. This ability not only gives you infinite mana but also an army of chump blockers, though when using Heartless Summoning you can't sac them for mana because they get -1/-1 counters before you can activate the ability.
The death:
There are four main cards that benefit from the infinite myr retriever combo, Disciple of the Vault, Falkenrath Noble, Bitter Ordeal and Pawn of Ulamog. Disciple of the Vault has target player lose one life whenever an artifact goes to the graveyard, so that's an auto win if you can play the combo. The issue is keeping him alive though, and he doesn't work with heartless summoning. However, he's a good one drop card if you've only got one mana left to play that combo. Falkenrath Noble is by far my favorite card to win with, as he's a 2/2 flyer and target player loses a life and I gain a life whenever him OR another creature, any other creature, dies. So he's great in multiplayer too especially. He's also a 2/2 and easier to keep alive and can work with Heartless Summoning. Pawn of Ulamog's ability is really to keep you alive with chump blockers and as much mana as you want until you get your combo. Bitter Ordeal lets you search a player's library for a card and remove it from the game. With the added ability of Gravestorm, which lets you copy that effect for every spell played before it during the turn, an infinite combo of playing myr retriever spells means you get to remove all of their cards, and since they can't draw, they lose.
Getting to infinity and beyond - playing fetch:
This deck wasn't really working until I added some black fetches in the form of Diabolic Tutor and Beseech the Queen, which let me search my deck for the cards I need for 4 and 3 mana, respectively. Beseech the Queen can be played for three black mana, but you have to reveal the card you draw, while Diabolic Tutor goes for 4 and you don't have to show. The Dark Rituals may be overkill in terms of mana, as I've ended up with two of them in my hand and no creatures to play, but they also allow you to use a fetch AND play the card you got same turn early on. Since this is a gimmick deck, if you've already got your other main players on the field that dark ritual can secure your win the turn you get the last card you need instead of waiting another turn. Arcbound Ravager is an expensive card, but I had one perchance and it works well to sac the Myr retrievers quickly, and you can also get infinite counters on him for attacking. However he's not really necessary due to the other mechanisms in the deck.
You must survive:
The biggest issue with this deck is holding out until you can play the combo. The Rathi trappers are 1/2's that you can pay 1B and tap to tap another creature, so they are cheap and great at screwing over powerful creatures who might do a lot of damage to you in those first few turns. Likewise,
Stinkweed Imp
(who might just be one of my favorite black cards ever) has deatchtouch and is a 1/2 and has flying, which makes him the perfect blocker for any and all creatures that may try to hurt you, as well as gets rids of them (as long as they dont have first strike). He also has the added advantage of Dredge 5, so you can put 5 cards into your graveyard, bring him back to your hand and play him for 3 again to once again do some blocking, AND if you only need one more Myr Retriever and already have the sac mechanism, if you put a Myr retriever into the graveyard with dredge and sac the one in your hand/on the field you can start the loop from the graveyard.
Weaknesses:
I would say this deck is most weak again blue, who can play spells to counter, kill or return the cards that trigger the win, like Falkenrath Noble, Disciple of the Vault and Bitter Ordeal, etc. Throwing in some Dash Hopes or Withering Boon would be useful, and I'm also looking to put in some removal as well. Bone splinter is a one drop but you have to sac a creature, not too bad considering the bonuses you get in this deck for creature death. Doom Blade and other two drops like it are good at destroying non black creatures, and for black creatures use the one drop like
Death Stroke
which is kill any tapped creature.
