The Sisters can petrify and steal your opponents' entire boards—IF they have enough mana. So the goal of this deck is to ramp as hard as possible to reach a state where the Sisters can take over the game.
Green is the undisputed champion of ramp, so you have plenty of options, including creatures like Yavimaya Dryad and Wood Elves who can block in the early game. Once you have all the mana, you can outfit the Sisters with Swiftfoot Boots, Nemesis Mask and Infiltration Lens. Then Charge your most dangerous opponent with your one-creature Wrecking Ball and take their toys.
The Commander's Quarters brews fun and focused Commander decks on a budget.