Rona, Herald of Invasion // Rona, Tolarian Obliterator

Two very different cards share one frame, and the front side is quietly the more interesting build. A 1/3 that untaps whenever you cast a legendary spell converts a modest loot (draw, then discard) into a repeatable engine: in a deck packed with legends, each cast is a fresh activation, so it filters your draws while the board fills with commanders and heroes. The tap ability is deliberately unremarkable on its own; the untap trigger is what turns it into a machine, and the legend density of the deck sets the rate. That the transform cost can be paid with life through the Phyrexian mana clause matters more than the mana number itself: it lets shells with no black source flip her anyway.

The back side is the flavor payoff and a genuinely unusual defensive design. Rona, Tolarian Obliterator punishes any source that deals damage to her, not just an attacker, by exiling a card at random from that source's controller's hand and handing it to Rona's controller (a land onto the battlefield, anything else cast for free). This is the wrinkle: it turns the act of removal against the remover. Point a burn spell at her or block her down and you feed the theft trigger with your own card, so combat damage and spell damage alike become liabilities. Trample keeps her a threat once flipped. The two faces sit at opposite ends of the card-advantage axis: one a slow selection loop, the other a theft engine that indicts every point of damage.