A budget version of Hydranix
The idea is to generate lots of mana with Arbor Elf/Voyaging Satyr + Overgrowth/Utopia Sprawl, then cast one of the big guys.
Replaced by Elder Gargaroth and Khalni Hydra.
This deck uses a sort of combo. How likely is a 'good' hand, where good means at least 1 untap elf, 1 forest and 1 of {Overgrowth, Utopia Sprawl}? Results (out of 100k simulations):
--- good hands ---
1 Mulligan, good only:
Good first try: 36165 (36.165%)
Good with mulligan: 53528 (53.528%)
Good after new mulligan: 59277 (59.277%)
Based on @Nescio's comment
This means you need 2+ Forests, an Arbor Elf, an Utopia Sprawl and an Overgrowth. Missing either a Sprawl or an Overgrowth is okay, as long as you have one of them. Missing a Forest is okay if you have the Arbor and a Sprawl, but it slows the deck down (you have 2 mana to spend turn 2 after playing Sprawl, instead of 4). Having a Voyaging Satyr instead of the Arbor is alright but again, it slows the deck down.
I wrote conditions for a 'great' hand and an 'okay' hand.
Great hand
hand.count(FOREST) >= 2 and hand.count(ARBOR_ELF) >= 1 and hand.count(SPRAWL) >= 1 and hand.count(OVERGROWTH) >= 1
Okay hand
enough_forests = ((hand.count(FOREST) >= 2) or ( hand.count(FOREST) >= 1 and hand.count(SPRAWL) >= 1 and hand.count(ARBOR_ELF) >= 1))
OKAY = (enough_forests and (hand.count(ARBOR_ELF) >= 1 or hand.count(SATYR) >= 1) and (hand.count(SPRAWL) >= 1 or hand.count(OVERGROWTH) >= 1))
With those conditions (which if you're still active around here, feel free to suggest any changes to), these are the odds of okay or great hands I calculated, by simulating 100k hands from the deck, with or without mulligan, + optionally after drawing one card.
No mulligan:
Great: 2026 (2.026%)
Okay: 26202 (26.202%)
1 Mulligan:
Great: 2588 (2.588%)
Okay: 39191 (39.191%)
No Mulligan + draw:
Great: 3831 (3.831%)
Okay: 33954 (33.954%)
1 Mulligan + draw:
Great: 3361 (3.361%)
Okay: 44909 (44.909%)
2 mulligan:
Great: 2703 (2.703%)
Okay: 45070 (45.07%)
All in all, almost half of the hands are at least OK if doing one mulligan if not okay initially, and it is really worth it after one draw.
