Even if one of the lands you sacrifice is both a Swamp and a Forest, you have to sacrifice another land that is a Swamp or a Forest
That's massive ramping, but it costs seven, but in a color that ramps lands not mana rocks, that could be a lot of value and seems doable
BPhillipYork: Flashback effectively being pasted onto all your spells is really solid
It does other things, but thats the ability you want
And the buyer protection policy covers you if something arrives damaged or not as described
While Martyr + [casthaven]Proclamation of Rebirth[/casthaven] is the engine to a more controlling build of Soul Sisters, here it is sacrifice this to turn on [casthaven]Serra Ascendant[/casthaven] or make target burn player cry. Its the most all-in card in this list and while it does synergize well with multiple cards in the deck, its the first thing I would cut if there were no budget considerations