Frost Mage PvE: Anomalus

“Anomalus is a giant Arcane Voidwraith boss in The Nexus. Voidwraiths are a slender type of voidwalker. Voidwraiths seem to be more rare than other voidwalkers and rarely talk.” - WoWWiki.com
Boss Stats:

Hit Points - 192,200
Mana - 50,000

Abilities:

Spark: Deals 2025 to 2475 Arcane damage.
Create Rift: Opens a Chaotic Rift near Anomalus which spawns Chaotic Wraiths.
Rift Shield [...]

Frost Mage PvE: Grand Magus Telestra

Grand Magus Telestra is a high elf, who is one of the Mages of the Kirin Tor who has sided with Malygos, in order to retain her arcane powers. She is one of the bosses of The Nexus, and could be the first you meet depending on which route your party decides to take.
“The Nexus, [...]

Frost Mage PvE: Prince Keleseth

“Prince Keleseth, of the San’layn, is the Scourge overlord of Howling Fjord and the ambassador to the Vrykul. Prince Keleseth is also the first boss of Utgarde Keep.
Utgarde Keep is the first dungeon hub located on the shores of Lake Cauldros in the Howling Fjord of Northrend. Inhabited by the Vrykul (led by King Ymiron), [...]