Merrow Commerce

The whole point of a tapping cost is that it spends the creature: an attack, an activation, a block declined. This enchantment hands one tribe a second swing at that economy. Untapping every Merfolk you control at the beginning of your end step means a "tap: do something" body can fire on your turn, untap as you pass, and stand ready to tap again during the opponent's turn (to block, to crew an activated ability, to feed a mana sink). The tap symbol stops being one use per turn cycle and becomes two: yours and theirs. Stack several such bodies and the end step is an engine, where mana producers refill before you pass priority and tappers reload to threaten interaction on the opposing turn. The cost is focus. It does nothing for non-Merfolk and nothing at all without a board of creatures whose tap abilities matter, so it demands a critical mass of relevant Merfolk before it earns its slot. That is precisely the deckbuilding gate a tribal payoff is meant to impose. It belongs to an older school of build-around enchantments that reward a committed creature type rather than slotting into a generic shell, the kind of card whose ceiling rises in lockstep with how deep the tribal commitment runs.