Miriam, Herd Whisperer

Two abilities that both solve the same structural problem for a mounted deck: the fragility of the vehicle-and-mount subtheme, where your payoff pieces spend most of the game as inert artifacts or vulnerable bodies waiting to be crewed. The offensive-turn hexproof is the more pointed of the two, because it targets the exact window when a Mount or Vehicle is most exposed. These permanents want to attack; that is when they generate value, and that is when the opponent most wants to point removal at them. Granting hexproof only during your turn threads the needle: it protects the swing without handing you a permanently untouchable board, so your opponent still gets their sorcery-speed answers on their own turn back. The attack trigger then compounds every hit into a growing threat, quietly turning a fixed-size Vehicle into something that outscales chump blockers over a few turns. The design reads as a lord built sideways: instead of the usual static +1/+1 to a creature type, it hands out a conditional keyword and a per-attack accumulation, both keyed to the act of attacking rather than to a tribe on the board. On a Selesnya body that costs two, that pairing asks the deck to commit to the aggressive plan and rewards it for keeping the pressure on, which is precisely the tension a Mounts-and-Vehicles shell needs resolved to function as a real archetype rather than a pile of clunky artifacts.