Sanctum of Calm Waters

The blue draw engine of the Shrine cycle, and the one whose payoff scales directly with how many Shrines you have managed to assemble. Every Shrine you control adds to the count, so this becomes a feedback loop: the wider your board of these enchantments, the more it refills your hand to keep the board growing. The discard clause caps that snowball; drawing four and pitching one still nets three, but it forces a decision each turn about what to shed, a decision that bites hardest when you are drawing into lands you no longer need or clutching something you would rather not lose. The "you may" does quiet work too: an empty library or a hand you would rather not touch lets you skip the trigger entirely, so the engine never decks you or strands you discarding your last card. Timing is the real constraint. It fires at the beginning of your first main phase, so unlike an instant-speed draw spell it commits you before the turn develops, and it cannot be held back to your end step to blunt an incoming wipe. What it offers in exchange is inevitability: a Shrine board left standing buries opponents in raw cards, and this is the piece that turns a slow enchantment shell into one that actually closes the game by drawing itself toward the win.