Noxious Field

The design idea here is putting a Pestilence-style damage engine onto a permanent that costs nothing to fire after the initial investment. Where Pestilence demands a black mana per ping and threatens to fall off the moment your board empties, this asks only for a tap of the enchanted land, turning a single untapped land into a recurring symmetrical machine gun. That is the trade: no upkeep cost, no mana drain, no risk of the engine sacrificing itself, but every shot hits you too, one damage to each creature and each player including its controller. The symmetry is the entire balancing discipline. Whoever runs this wants a slow, attritional black deck that can outlast the clock it sets on itself, either by gaining life, by playing creatures that survive a steady drizzle of pings, or by simply racing the opponent to zero from the safe side of a board where its creatures are bigger. The pinging-the-land detail matters more than it looks: because the ability lives on the land rather than on a creature, it dodges most creature removal entirely, and an opponent has to answer the aura or the land underneath it rather than killing a body. The result is a permanent, hard-to-remove source of repeatable damage for a deck willing to bleed alongside its opponent to keep one online.