The "right" way to 1-land Spy!
The "short" explanation:
You Spy into Songs, then you use Morgue Theft on Pit Keeper and Morgue Theft a Blood Celebrant. Then you cast Pit Keeper targeting Cavern Harpy, cast the Celebrant, cast the Harpy off of Celebrant mana, bounce your Pit Keeper and recast it targeting Mnemonic Wall. Then you use the Wall to target Songs of the Damned and you can make a bunch of mana here continuing to bounce the Harpy and Wall repeatedly. Next, get Gary out of the yard with the Pit Keeper + Cavern Harpy trick. Use this mana with Cavern Harpy and Gray Merchant of Asphodel to drain the opponent out. You can also bounce and re-cast Balustrade Spy every couple loops to mill them out as well. It is long and convoluted, but it works.
How the combo "works" (i.e. the LONG explanation):
Key - [Mana] +/- Life
You can go off when you have: Untapped Forest on board. Spy in hand, and a way to get songs - either it's in your hand, or you have a bauble in play, or one in hand and an extra mana. 4 other mana, 2 of of it B. At least 5 life.
-Start. [3BB] -0
-Play Spy, targetting you. [B] -0
-Play Songs. You need this to make at least 23 Mana. You have 29 creatures. Minus Spy that leaves, best case, 28 Mana off Songs. Be careful! [23xB] -0
-Flashback Morgue Theft targetting Pit Keeper. [18xB] -0
-Play Pit Keeper, returning Blood Celebrant. [16xB] -0
-Play Blood Celebrant. [15xB] -0
-Flashback Morgue Theft targetting Cavern Harpy. [10xB] -0
-Change B to U using Blood Celebrant. Play Cavern Harpy, returning Pit Keeper. [8xB] -1
-Play Pit Keeper, returning Mnemonic Wall. [6xB] -1
-Change B to U using Blood Celebrant. Play Mnemonic Wall, returning Songs. [B] -2
-Play Songs. Worst case, at this point you now have 19 creatures in your yard. Now we need to set up the Gray Merchant loop.
You must do a secondary prep loop to prepare your steady-state. Your steady board state (the start of each of the combo loops) looks like (again, worst case scenario):
Tapped Forest, Balustrade Spy, Blood Celebrant, Pit Keeper, Cavern Harpy, Mnemonic Wall, Gray Merchant of Asphodel.
The rest of your deck in your graveyard, including only 18 creatures and no Morgue Theft.
-Secondary Prep loop:
--Start [19xB] -2
--Return Cavern Harpy to hand. [19xB] -3
--Change B to U using Blood Celebrant. Play Cavern Harpy, returning Pit Keeper. [17xB] -4
--Play Pit Keeper, Returning Gray Merchant of Asphodel. [15xB] -4
--Play Gary. [10xB] +2
-At this point, you will need to 'Make Mana', then 'Gain Life'.
-As long as you have 3 Life and 8xB to pay, going through 'Make Mana', then 'Gain Life' will net you +1 Life and at least BBB each iteration, as well as 6 life loss to opponent.
-Every 2 times through 'Make Mana', then 'Gain Life', you will gain +2 Life and 6xB, enough to pay for one iteration of the second win condition, if you desire.
--=Make Mana=--
Pay: 3 Life and 8xB --> Gain: 18xB
-Return Cavern Harpy to hand.
-Change B to U using Blood Celebrant. Play Cavern Harpy, returning Mnemonic Wall.
-Change B to U using Blood Celebrant. Play Mnemonic Wall, returning Songs of the Damned.
-Play Songs.
--=Gain Life/Win Condition 1=--
Pay: 2 Life and 7xB. --> Gain: 6 Life. Opponent loses 6 Life.
-Return Cavern Harpy to hand.
-Change B to U using Blood Celebrant. Play Cavern Harpy, returning Gray Merchant of Asphodel.
-Play Gary.
--=Win Condition 2=--
Pay: 2 Life and 6xB. --> Gain: Mill Opponent to next land.
-Return Cavern Harpy to hand.
-Change B to U using Blood Celebrant. Play Cavern Harpy, returning Balustrade Spy.
-Play Spy.
