Conjurer Mage is an archetype that’s new to Rise of Shadows, although some of the core cards are older. What activated them, however, is a new spell – Conjurer's Calling (and that’s where the deck’s name comes from), which is basically the centerpiece of this entire build.
One of the deck’s main win conditions is dropping an early Mountain Giant (thanks to Book of Specters which lets you draw 3 cards for just 2 mana – assuming you don’t run many other spells to interfere) into Conjurer’s Calling, which summons two of them (or Grave Horrors, which share the mana cost). Even better if you also have Khadgar – now you summon 4 huge minions in total and probably just win the game. Later in the game Conjurer’s Calling can be combo’d with other minions too, or you can win through the pressure provided by Dragon package.