Affinity is an artifact-based aggro deck that wants to flood the board with cheap threats like Pinnacle Emissary and Kappa Cannoneer, so cheap removal and targeted artifact hate go a long way. Nature's Claim is excellent against their Mox Opal, Engineered Explosives, or a resolved Weapons Manufacturing engine, gaining you tempo for one mana at instant speed. The extra Unholy Heat gives you efficient removal for their small creatures (Pinnacle Emissary 3/3, Emry 1/2) and even Kappa Cannoneer if delirium is online. A second Vexing Bauble punishes their many zero-cost or improvise spells like Mox Opal activations aren't spells so it mainly stops things like a hard-cast Preordain being free is irrelevant, but it's a fine speculative include against a low-curve deck. Writhing Chrysalis and Haywire Mite are cut since they're too slow against Affinity's explosive starts, and Soul-Guide Lantern/Pithing Needle have minimal impact on their gameplan.