Subterranean Spirit

A repeatable pinger built on an asymmetry that bites everything except the one thing it cares most about. Protection from red means the tapping ability rakes the board for one without ever singeing the creature itself, and that immunity also makes it a clean blocker against red attackers and a hard target for the era's deep well of red burn. The damage clause is the design lever doing the real work: it hits each creature without flying, so it sweeps the ground for weenie hordes and token armies while leaving fliers (often the more expensive, more valuable bodies) untouched. That carve-out turns a slow, repeatable wrath-on-a-stick into an asymmetric one, rewarding a board built above the line it draws. And because the damage comes from a tap ability rather than a sorcery, once the body is past summoning sickness it can be activated at any point you hold priority: tap it end-of-combat to mop up an attacker that survived blocks, or hold it for the opponent's turn. The threat is attritional but not passive: untap, ping, repeat, and watch the small stuff erode, with the timing left to whoever reads the board best. It belongs to a Mirage-era school of red design that paired aggression with grind, a single permanent that asks the opponent to either go wide and get whittled or go tall and over-commit. The protection keyword is the elegant part: it solves the mirror, the burn problem, and the blocking math in one line.