Class: Lich

The Warcraft story:
During his mortal life as the Warchief of the Orcish Horde of Draenor; Ner'zhul commanded a number of Orcish Warlocks and Shamans. Yet, when these wicked sorcerers were captured by Kil'jaeden and the Legion after the destruction of Draenor, they were transformed into twisted aberrations of their former selves. These Liches possessed tremendous magical powers, yet their immortal, undead bodies were bound to the iron will of Ner'zhul. Since the Liches showed unswerving loyalty to their master, Ner'zhul granted them control over the furious elements of the cold north. Now, Liches wield frost magic along with their own considerable necromantic spells.

I belive that its a good thing that the Liches does command the Frost and Ice elements and abilities, cause it fits to their nature, a walking, practicly flying, magic pile of bones!
The Liches was some of the first to discover how to revive or reanimate the Dead, but this ability is long lost and forgotten by the most Liches, cause that their Lord, The Lich King, had other plans with them. Both that they got granted the power of Ice but also that the most Liches are used in greater summonings or Magic Portal Openings, like seen in Warcraft! Therefor they passed the mighty spells of reviving units into Undead Soldiers, on to the Necromancers of the Temple of the Damned!

The R.P.G. story:
Mostly there are no Liches in normal Roleplaying Games, if there finnally should be any Undead creatures then they are most just commented as either Dark Wizards, Zombies, Ghouls or Skeletons!