http://www.wizards.com/Magic/Magazine/Article.aspx?x=mtg/daily/arcana/981

As the sensei of the "Night of the Ninja" deck, you're in control of a cadre of sneaky Ninjas. Early in the game, you'll need some stealth agents. Cast cheap little creatures with evasion like Tormented Soul and Dimir Infiltrator, then start to attack. Pick your spots carefully, making sure your attacking creatures won't get blocked, then—surprise!—use the ninjutsu ability of a Ninja in your hand to replace an unblocked attacker! You'll deal more damage, get the Ninja's bonus, and wind up with the original attacker back in your hand. If that creature provides a benefit when it enters the battlefield, like Augury Owl and Baleful Strix do, you'll get that benefit again!

All these bonuses add up over the course of a game. In particular, Silent-Blade Oni and Ink-Eyes, Servant of Oni can devastate your opponents by stealing their cards right out from under them! If the battlefield gets too crowded late in the game, Vela the Night-Clad and Higure, the Still Wind can still let your Ninjas sneak past your opponents' defenses to deliver the finishing blows.

The cards in your planar deck are no less wily. Takenuma lets you draw a card each time you use a ninjustu ability (or one of your creatures leaves the battlefield in any other way). Glen Elendra lets you trade your smallest evasion creature for your opponent's biggest beater. Bloodhill Bastion is particularly devastating with Ninjas, as they'll all show up with double strike. And Kharasha Foothills duplicates all your attacking creatures, sending them at all opponents at once.