Betrayal

A blue mage's bet on the opponent's own deck. Sticking this on a creature an opponent controls turns their attacks, their mana dorks, their tap-to-activate abilities into draw steps for you, which means the card's value is entirely a function of how much their board wants to do things. That is the wrinkle: it does nothing on its own and demands a target whose behavior you cannot dictate, so it rewards reading an opponent's plan rather than executing your own. The friction is what keeps a one-mana repeatable draw engine honest. Against a creature that sits back, this is a dead card; against one that has to attack or tap to function, it bleeds cards out of the matchup turn after turn. The design works as a "punish them for using their stuff" Aura, converting an opponent's tempo into your card advantage. It is parasitic in the literal sense, drawing its fuel from the host's activity, and the cleverness is that the opponent rarely gets to simply stop tapping the enchanted creature without conceding a different advantage: a mana dork that never taps is dead mana, an attacker that never swings is a wasted body. A one-mana enchantment that asks the opponent to choose between their game plan and your card draw is a tidy bit of asymmetry, even if it never found a deck that could reliably guarantee the trigger.