Duskmantle Seer is one of the newest "Magic: The Gathering" cards spoiled today Jan. 17, 2013 from Wizards of the Coast's upcoming expert expansion set "Gatecrash." Revealed in an article by Mike Flores on MagicTheGathering.com, Duskmantle Seer provides card advantage and can damage your opponent at the same time.
Duskmantle Seer - 2UBCreature - Vampire Wizard (Mythic Rare)
At the beginning of your upkeep, each player reveals the top card of his or her library, loses life equal to that card's converted mana cost, then puts it into his or her hand.
Duskmantle Seer is an interesting Dark Confidant variant that
affects your opponent too. Because you can build your deck around it though, you'll have the upper hand. By playing with a low mana curve or with cards that allow you to manipulate the top of your library you'll be able to minimize your life loss.
Because your opponent doesn't get the card on their turn an easy solution might just be to make them discard the card they just revealed with Duress, Liliana of the Veil, Triumph of Cruelty, or Rakdos's Return.
Another idea is to use the information you've gleaned from Duskmantle Seer to name key spells with Slaughter Games or Nevermore. In older formats you can use more mana efficient spells like Surgical Extraction.
One way to take advantage of Duskmantle Seer is in a Vampire deck. Vampire Nocturnus can pump Duskmantle Seer while also letting you know what's on top of your library. If you're not willing to pay four life for an Olivia Voldaren or Falkenrath Aristocrat, simply stick it in your graveyard with Codex Shredder during an opponent's turn to help find a cheaper card or land. After you've drawn for your turn on you'll be able to use Codex Shredder to ensure there's a black card on the top of your deck or return a removal spell like Dreadbore to your hand. Vampire Nighthawk can help you recoup your life loss and Stromkirk Captain can pump all your vampires, including those early drops like Stromkirk Noble.