Cursecatcher

A one-power body that doubles as a soft counter, built to tax the spells that would unravel a board of small blue creatures. The sacrifice clause is what makes it more than a Merfolk lord-feeder: it can apply to the clock until the moment an opponent reaches for a sweeper, a burn spell, or removal aimed at the lord that matters, then convert itself into a tempo tax at no mana cost. Force Spike does this once and then it is gone from your hand; here the tax rides on a creature that contributes pressure first and disrupts second, so the cost of keeping it live is a sacrifice you were always willing to make, not a card held in reserve. The "unless its controller pays " wording is deliberately a tax rather than a wall: it does not stop a committed opponent, it makes the spell arrive a turn late or get squeezed for an extra mana the curve cannot spare. That fits the aggressive shell it was made for, where the tribe is already racing and one stalled removal spell is enough to close. The threat does as much work as the ability: an opponent who sees a Cursecatcher in play, and knows it costs nothing but the body to fire, has to weigh whether their key instant or sorcery is worth handing over that mana on this turn rather than a safer one.