Boros Energy fills the board with small, fragile bodies like Guide of Souls, Ocelot Pride, and Ajani, Nacatl Pariah, so Searing Blaze is excellent removal that also burns their face. Pyroclasm sweeps their 1/1 and 1/2 tokens and creatures for a huge tempo swing. Rain of Gore turns lifegain from a spell or ability like Guide of Souls' trigger into life loss for its controller, while Skullcrack stops lifegain for the turn from sources like Ocelot Pride's lifelink and adds reach. Eidolon of the Great Revel is risky since casting your own cheap spells pings you while they can gain life, so it comes out along with lands to make room.