Heartstone

A cost reducer for activated abilities, built with the same caution Wizards has always applied to discount engines: the floor clause that keeps any ability from dropping below a single mana. That restriction is what makes the card safe to print. Without it, every free-or-near-free activation would chain into an arbitrary loop the moment the discount stacked with a second copy or a mana producer that taps for its own ability. The floor turns Heartstone into a flat shaver rather than a combo enabler: it pays for itself across a board of creatures with repeatable activations, but it never breaks the math on a single one. The card does for a whole battlefield of pingers, untap-engines, and tap-down dorks what a generic spell-cost reducer does for a hand of cards, lowering the per-use rent on activations en masse. What dates it is the symmetry: the discount applies to every player's creatures, so it rewards being the side with more activations on the table rather than locking the benefit behind your own colors. That makes it a build-around rather than a default include, a piece you reach for when your deck is already a hum of repeatable activated abilities and the per-activation mana is the bottleneck.