@shocker300

Just because Harrow doesn't do too well against blue doesn't mean it's a bad card. Last time I checked, some decks aren't blue.

One little trick you can do with Harrow in a green-blue deck is to make people think that you can't counter their spells when, because of Harrow, you can. For example, lets say you have Harrow and Cancel in your hand. You have three forests and one island untapped. The opponent might think that you can't counter their game-changing creature, so they cast it. In response, you cast Harrow, search for enough islands that you can cast Cancel, then cast it.