Blood mage

Mystical heroes, blood mages (a.k.a. bloodmages, sometimes blood magi or bloodmagi are blood elves adept at controlling magic and ranged assault. While they were still members of the Alliance, the blood elves began to turn to the darkest parts of magic, abandoning the water and frost spells of the Kirin Tor for the fire and heat of what some people fear to be demonic magic.

The most famous and the first of the blood mages was Kael'thas Sunstrider, the Prince of Quel'Thalas. He commanded the blood elves after the death of his father Anasterian, leading them out of the Alliance and into Illidan's service.

Blood magi are present in Quel'Thalas being commanded by Grand Magister Rommath.

Origin
Many of the stoic high elves, reeling from the loss of their ancient homeland, Quel'Thalas, have given in to their hatred and despair and embraced the dark side of their magical natures. Calling themselves "blood elves", these cold hearted refugees seek to expand their remaining magical powers at any cost — even if it means courting the infernal powers of the Burning Legion. Though still loyal to the Alliance, the blood elves' passions will lead them not only to the highest pinnacles of power, but to the darkest depths of madness.

Abilities
Blood mages have many abilities based on the usage of fire and mana.
 * Flamestrike
 * Banish
 * Drain Mana
 * Summon Phoenix: This ability is mastered by few blood magi, the one known is Kael'thas Sunstrider.

They can use numerous other spells such as Fireball or Pyroblast.

Verdant Sphere
Verdant Spheres seem to be orbs of magical fire that revolve around the head of some blood mages. Rumor has it that they siphon the life essence of the demons slain by the blood mage, further empowering especially their fire spells. In Warcraft III, the playable blood mage hero flung a Verdant Sphere whenever he cast a spell or attacked an enemy.

In the novella Blood of the Highborne, it was revealed that Prince Kael'thas Sunstrider's Verdant Spheres were originally the three guardian Mooncrystals of Quel'Thalas which were corrupted within the Scourge-ridden waters of the Sunwell. This may prove to counter the idea that every blood mage owns one or several Verdant Spheres due to both the rarity of the initial Mooncrystals and the sheer amount of power that the corrupted Sunwell held to change them. It may also mean that Verdant Spheres owned by others such as Varanis Bitterstar are simply not as empowered as the ones owned by Kael'thas himself.

Human

 * He has been updated in Mists of Pandaria and is now known as Thalnos the Soulrender seeming to be more a necromancer than a blood mage.

Other blood magi
Eldin Sunstrider, Tanin Hawkwing, Lorn Bloodseeker, Aldos Firestar, Gilaras Drakeson, Hale Magefire, Kath'ranis Remar, Tyoril Sunchaser, Sylvos Windrunner, Marakanis Starfury, Geldor Earthfire, Halendor Burnkin, Kelen the Destroyer.

Speculation

 * Near to the end of the Purge of Dalaran events in Patch 5.1.0, Regent Lord Lor'themar Theron orders Grand Magister Rommath to "assemble the blood magi" in order to prepare for the up and coming assault on the Isle of Thunder. This would lead one to assume that the ranks of the Magisters beneath him include several.
 * As he uses fire spells and can summon phoenixes, Jeron Emberfall might be a blood mage.