Thoughtleech

Notice that the trigger keys off tapping rather than the Island merely existing, and you find the one design choice that gives this thing teeth. It does not tax the manabase; it taxes the act of playing blue. Every counterspell cast, every card drawn, every Island turned to fuel a threat pays you a point of life. That is a tempo tax dressed as a land tax, and it punishes a deck for doing the very things blue decks want to do. The numbers are almost beside the point: one life per tap is a trickle, and against a deck with no Islands at all this enchantment sits inert until the game ends. The wager is the whole pitch. Color-hosing enchantments from this period worked this way: Karma drained life from Swamps, and others sat aimed at Mountains or Plains, each justified only by how lopsided a matchup it could swing when the read was right. The cost of dedicating a card to so narrow an answer was paid back in matchups that became unwinnable for the opponent once the answer connected, and bricked entirely when it did not. Thoughtleech asks you to bet on what your opponent's deck is made of, and to live with the blank when you bet wrong.