The arrival of the necromancer was predicted in the last year, when Blizzard announced that some characters and objects in Diablo 2 were being reinvented for Diablo 3 BlizzCon . The company announced some abilities of the character last month, but now is already in the closed beta, and if you are lucky you could try.
The beta of the new necromancer character is in closed version, so at the moment, the only way to access it is still a beta-tester of Devil through your Battle.net profile settings, and then I would only be expected with much hope, that the email reaches us announcing that we are the chosen ones. Blizzard will also invite “key members of the community” to participate, so if you fit the profile, might also have luck in that way.
Test beta not only includes the necromancer, they also all the other contents of the patch 2.6.0, including new challenges, two new areas for the Adventure mode, improvements in the Set dungeons, and four new events in Act 4, each with new rewards to complete.
If you want to read a more detailed breakdown of the powers of the necromancer, with the warning that all is still in development so that “the two numbers and functionality can continue to be subject to substantial changes”, is in the official statement of battle.net .