Grave Keeper

The Grave Keeper (a.k.a. the Necromancer) is the announcer for two battlegrounds: the Haunted Mines, and the right side of the Towers of Doom. He also appears as an unlockable announcer in Heroes of the Storm.

Background
The Grave Keeper is a creepy-sounding necromancer living in an area on the outskirts of Raven Court called the Haunted Mines. His appearance on his Core is a hooded humanoid with green-glowing eyes, a massive pair of antlers and a scythe.

Haunted Mines
The Grave Keeper drove the Raven Lord out of the Haunted Mines, and after some "redecorating," re-opened them. He makes a deal with the player(s) in an effort to gain more power : Whenever he opens the mines, he'll create a bone golem for either team and send them against the enemy's fort once all the skulls have been collected from the undead miners deep underground.

Towers of Doom
On Towers of Doom, the Grave Keeper employs the service of heroes to destroy the Raven Lord and claim dominion over Raven Court.

In order to overcome the Grave Keeper's rebellion at the Towers of Doom, the Raven Lord summoned beings from the Dark Nexus, setting them loose upon the Grave Keeper's forces. After the Grave Keeper's domination by the Raven Lord, Spectral Wyrm Alexstrasza pledged her phantoms to his side.

Trivia

 * The Grave Keeper used to be named 'The Necromancer' (according to his sound files), but his name was revealed to be 'Grave Keeper' at Blizzcon 2015 and the arrival of the Tower of Doom. It might be to differentiate him with the actual Necromancer, Xul, who's announced after the Blizzcon 2015 heroes batch.
 * Apperently, the Grave Keeper made an unholy alliance with Grave Warden Malthael.
 * The original concept art of the Grave Keeper was done by Samwise Didier: "I was listening to a lot of Doom Metal at the time and created this image based off the music from new band Wretch. I ended up using the art for the Grave Keeper since it was cool looking and was already done. And this is why I always say to artists, ABC, Always Be Creating, One never knows when some image created for fun, can turn into something millions will see."