Song of Inspiration

Regrowth for two permanents is the floor here, and it is a fine floor. What the d20 layers on is a scaling reward keyed to exactly the cards you were retrieving anyway. Because the roll adds the combined mana value of your two targets, the lifegain threshold isn't a fixed number but a moving one that a graveyard full of expensive permanents closes on its own. Bring back two five-drops and a 5 or better clears 15; grab the right pair of bombs and the die can barely fail you. The instant speed is doing quieter work than the effect's power level suggests: this is held-up recursion, a two-card return you can float in reaction to a wrath resolving or a piece dying, rather than a sorcery-speed commitment. The lifegain is genuinely incidental, a rider that pays you for stocking a graveyard with big permanents rather than a payoff worth building toward. That is the honest read: a solid two-card graveyard return with a die roll bolted on to make it feel like an event. The recursion is the reason to run it; the d20 is the dice-rolling texture of its design lineage stapled onto a green staple whose ancestors go back to the earliest sets.