Glistening Oil

Infect on demand, repackaged as a recurring threat that refuses to stay dead. Most ways to grant infect ride on a creature: the creature dies, the poison engine dies with it. This one decouples the keyword from any single body. Stick it on something, swing for poison counters, and when the host inevitably succumbs (to the upkeep -1/-1 counter that ticks it toward zero, or to removal aimed at the threat), the Aura bounces back to your hand to suit up the next attacker. The self-buyback is the load-bearing trick: it turns a fragile one-target enchantment into a reusable poison delivery system an opponent cannot answer by killing the creature, only by racing the clock. The catch is that the same upkeep counter eroding your host gives each enchanted creature a built-in shelf life, so the card wants a stream of disposable bodies more than one prized carrier. That tension, free recursion against self-inflicted decay, is the design's center of gravity: rather than a strictly-better way to splash infect, you trade board presence for inevitability, shrinking your own creatures to keep the poison clock running. It is the Phyrexian-compleation idea expressed as an attachment rather than a creature, the corruption literally migrating from host to host.