Blessing of Leeches

Free regeneration is black's oldest defensive trick, but it usually came attached to a creature you didn't want or a one-shot instant you had to keep redrawing. Pinning it to an Aura with a zero-mana activation turns a single creature into a recurring brick wall: as long as the enchantment stays put, the body shrugs off burn, lethal combat, and targeted destruction, again and again, for no further mana. The upkeep life loss is the meter running on that protection, a slow drain that taxes you for keeping a fragile body alive past its usefulness rather than capping how many times you can save it. Flash is what gives the deployment its timing flexibility: the Aura still costs three mana to cast, so an alert opponent can read the open mana, but you are not forced to commit it on your own turn. You can wait until a removal spell is on the stack or a block is declared, then attach in response and regenerate at instant speed, leaving the opponent's spell to resolve against a body that simply refuses to die. The cost is structural rather than numeric. Regeneration does nothing against exile, sacrifice, or minus-toughness effects, so the shield is only as durable as the era's removal suite, and the life payment compounds whether or not the protection is ever needed. It is a conditional answer dressed as permanent insurance, and the bill comes due every turn.