A-Mightstone's Animation

The trade this Aura makes is the one that separates it from every animation effect that came before: it doesn't just turn an artifact into a creature, it pays you two cards up front to soften the tempo hit. Animating an artifact has always been a fragile plan (spend a card, buff a permanent, watch the whole investment die to a single removal spell), and the loot on the enters trigger is the concession to that fragility. Even if the enchanted artifact is answered the moment it becomes a 4/4, you've already replaced this card and dug a card deeper. The design leans on which artifact you point it at. On a Mishra's Bauble it's overkill; on a mana rock, a Signet, or a mox it turns a piece of your board that was never going to attack into a body with real stats, adding a threat without adding another spell to the count. The card-filtering front-loads the value so that the animation itself becomes upside rather than a liability, a quiet acknowledgment that the classic "enchant your rock and swing" line has always been a card down before the first attack step.