text: When the enchanted artifact becomes tapped, Relic Putrescence’s ability triggers. The player who gets the poison counter is the player who, at the time the ability resolves, controls the artifact that became tapped. If that artifact is no longer on the battlefield, its last existence on the battlefield is checked to determine its controller. It doesn’t matter whether Relic Putrescence is still on the battlefield as the ability resolves, what artifact it’s enchanting at that time, who controlled the artifact at the time it became tapped, or who tapped it.