Crumble

The lifegain rider does the work a plain Disenchant variant never had to: green answers anything in an artifact-heavy field for a single green pip, but pays the artifact's controller back in life equal to its mana value. That payment scales with the threat. Destroy a Mox and your opponent gains nothing, since its mana value is zero; destroy something expensive and you hand back a life total that climbs with the rate. The asymmetry is the point, and it is the lever that kept this from being a free upgrade over the rest of the era's artifact destruction. Compare it to Shatter, a red answer that charged two mana and paid nobody: green's version undercuts that on cost outright, so the lifegain was the design tax that justified pricing a flexible artifact answer this low. The lifegain-as-tax model never fully disappeared from green: Nature's Claim later carried the same idea, handing the controller a flat four life regardless of what it destroyed. But the trend over time was toward unconditional rate, with answers like Naturalize dropping the rider entirely. This is the transitional artifact-hate spell: green learning to hate artifacts before green was sure it was allowed to, and pricing the privilege in someone else's life total.