Herd Heirloom

Two mana rocks sharing a body, except only one of them actually makes mana. The first ability is restricted ramp: any color, but the mana vanishes unless it feeds a creature spell, a leash tight enough that the rock never quietly becomes color fixing for the whole deck. The second ability is where the card earns its keep. Green has always had the trample and the fatties; what it historically lacked was a clean, repeatable way to convert connecting damage into cards without splashing blue or leaning on a dedicated enchantment. Handing trample and a draw-on-combat-damage trigger to any single big creature, once per turn at instant speed, folds both jobs into one permanent that already tapped for ramp on the turns you did not need to swing. The power-4 floor is the honest gate: this is built to make an already-threatening body harder to chump and turn its hits into resources, not to reward a wide board of small creatures. The design reads as a deliberate synthesis of two roles green midrange usually splits across separate cards, ramp early and card advantage later, sharing a body and a tap symbol so the same rock stays relevant from the turn it drops through the alpha strike.