Boros Energy is full of small, high-impact creatures (Ragavan, Guide of Souls, Ocelot Pride, Voice of Victory) that Unholy Heat answers efficiently, especially once delirium turns it into a 6-damage blowout on bigger threats like Ajani or Boromir. This matchup is a damage race, so Assault Strobe can close games quickly by giving a Monastery Swiftspear or Dragon's Rage Channeler double strike for a sudden lethal swing. Mutagenic Growth is a weaker trick here since their removal (Galvanic Discharge) scales with energy and can still kill a pumped creature, and one Mishra's Bauble can be trimmed since card selection matters less than board presence against their proactive clock. Watch out for Blood Moon turning off Steam Vents and other duals, so sequence lands to play around it when possible.