Slay the Spire poses problems to you and asks you to solve them, with one of the main problems being "can you deal enough damage to kill these enemies within a certain timeframe?" In any run where you're struggling to answer that problem, Rolling Boulder is a single card which fixes that for you almost on its own. One of these, unupgraded, deals 225 damage over 10 turns. Decks which otherwise have no business ever killing a Boss are suddenly able to do so easily.
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