Urborg Stalker

A color hoser dressed up as a creature, and one of the more committed thematic statements the early sets made about black's idea of purity. The whole school of upkeep-tax cards (the ones that ping or drain at the start of a turn) usually fires at everyone or just the opponent; this one checks each player's board individually and punishes only those who control a nonblack, nonland permanent. The premise of any symmetrical hoser is that the controller builds to dodge it, so a mono-black deck running the Stalker pays nothing while every off-color opponent takes a steady tax for the sin of a white enchantment or a green mana dork. The punishment is the flavor: live inside Urborg's black-mana hegemony and the creature leaves you alone; bring anything foreign and it bites. What keeps the effect from ever being a real clock is that the trigger re-evaluates state at each upkeep rather than locking in. A player taking the damage can simply stop controlling the offending permanent (sacrifice it, bounce it, let it die) to shut the trigger off, so one point per qualifying upkeep stays a nuisance rather than a threat. The 2/4 body offers no second axis beyond blocking. It is a curiosity from the era when Wizards still built creatures around narrow color-hosing hooks rather than reliable rates, and the hook here is specific enough that the card only ever made sense as a thesis about which permanents Urborg tolerates.