Bile-Vial Boggart

A one-mana body whose value is entirely deferred: the counter lands only when the creature dies, which turns the goblin from a card you spend into a card you position. The -1/-1 counter is the sharp part of the design. It shrinks a creature permanently, so an X/1 dies outright and an X/2 becomes trivial to finish, but it also erases a +1/+1 counter or trims a creature back under a toughness-gated effect. Because the trigger keys off dying rather than combat, a chump block, a sacrifice outlet, or a favorable trade all cash the same dividend, and the "up to one" clause means you never have to fire it into a board where the counter would be wasted. That structure rewards a deck already built to feed the graveyard: the goblin wants to be blocked, wants to be sacrificed, wants to trade down, because every one of those outcomes is the card doing its job rather than the card dying. It is a small, patient piece of black attrition, closer in spirit to a removal spell stapled to a speed bump than to an aggressive one-drop, and its ceiling is set by how reliably the rest of your deck can arrange for a 1/1 to die on your terms.