If you're in command of the "Spectral Legions" deck, you're in command of the afterlife. Spook your opponents with a cadre of flying ghosts blessed with divine powers. Your victory will haunt them for days!
The bulk of the deck is made up of evasive Spirits. Most have flying and the rest have intimidate, so they'll be difficult to block. Your best plan is to be aggressive, attacking with creatures your opponent can't block. While doing so, bolster your attacking Spirits with Auras like Curiosity, to help you draw more cards, or Lifelink, to help you gain life.
Defensive help comes from Auras like Pacifism and spells like Unsummon keeping enemy forces at bay. Enchanting one of your creatures with Spirit Mantle or Divine Favor makes that creature a fantastic blocker.
Your knowledge of the afterlife isn't restricted to creatures that have Spirit printed on their type line. When Doomed Traveler and Mausoleum Guard die, Spirit tokens take their place and continue to fight for you. Angel of Flight Alabaster, meanwhile, lets you recover fallen Spirits from your graveyard. With this deck, death can't hold the dead for long.
One way to pump this deck up is Dearly Departed, a 5/5 flying Spirit that continues to have a major impact on the battlefield long after it's dead. Mindshrieker is a two-mana flier that can hit for major chunks of damage while depleting an opposing library. Also consider Adaptive Automaton from the Magic 2012 core set, a creature that can give your Spirits a substantial +1/+1 boost.