Yesterday saw the reveal of two Mage cards, Servant of Yogg-Saron and Faceless Summoner. There have now been sixty three cards revealed. Blizzard have announced a live stream on April 21, and it seems likely we will get a mass reveal on that date.
Faceless Summoner is an efficient way to put a lot of stats on the board. Although the summoned card will not trigger Battlecry, the Summoner still represents value in its most raw form. It seems likely that this will be a very highly picked Arena card, especially with it being common, and will see testing in Aggro and Value Mage Standard decks.
Servant of Yogg-Saron is another Mage card with a random effect. For it to be of value, the Battlecry will need to be worth about 1 mana. Although the randomness will be a net positive due to cards that don't target, such as and , it will likely not be consistent enough to see constructed play even if it covers the 1 mana of value.Deathwing - Dragonlord and Embrace the Shadow .Thistle Tea and Twilight Summoner .Wisps of the Old Gods and Soggoth the Slitherer .Cho'Gall and Possessed Villager .Yogg-Saron and Spreading Madness, plus lore .Blood Warriors and Call of the Wild .Hammer of Twilight, Mire Keeper, Blood of The Ancient One .