Heal the Scars

Regeneration was once green's signature trick, the shield it threw over a creature to walk it through combat or a sweeper, and this is the variant that asks the regenerated body to pay you back. The lifegain is keyed to toughness, which is exactly the stat regeneration cares about: you tend to protect your durable blockers, the high-toughness walls and beaters that survive trades anyway, so the second clause turns a defensive reflex into an incidental life swing. The trouble is that the two effects pull in opposite directions on the curve. Regeneration is a reactive, instant-speed insurance policy you hold up and would rather never spend; the lifegain rewards you for committing four mana at a chosen window. At four mana for a single-creature shield, the rate sat below the era's combat tricks even when it was new, and stapling a toughness-sized life payment onto it never closed that gap. Modern green protection has largely abandoned the regenerate keyword entirely (indestructible and hexproof do the work now, and they dodge the wraths regeneration could not), which leaves this as a fossil of a design language the color has mostly moved past. What it does at its best is answer one removal spell or combat trick one-for-one, keeping your biggest creature on the table while skimming a healthy chunk of life off its toughness in the process: a fair trade, not a card-advantage swing.