Death knight

In fantasy literature and role-playing games, a death knight (sometimes referred to as a shadow knight or dread knight) is an undead corruption of a righteous warrior who broke his or her code of honor and embraced evil.

Warcraft
In the Warcraft Universe, Death Knights were paladins killed and raised from the dead by an Orcish necromant called Gul'dan.

In Warcraft games they were portrayed as:
 * 1) The primary spellcasting unit of the orcish Horde in Warcraft II.
 * 2) A warrior hero of the undead race in Warcraft III.

Dungeons & Dragons
In Dungeons and Dragons a death knight is a mighty warrior resurrected as an undead creature by the gods of death in order for it to lead as a general of undead armies. A paladin or lawful good warrior can also become a Death Knight after being cursed by the gods for committing a particularly evil act or betraying the code of honor it held in life.

Death Knights often have a variety of undead servants such as Skeleton Warriors, Liches and Banshees.

A Death Knight retains its personality from its former life. It is condemned to remember its downfall through song on any night when the moon is full. Sometimes the chilling melody is sung by musically-inclined servants instead of the Death Knight itself. Whilst the song is being sung, the death knight will ignore the outside world, unless the song is disturbed, causing the knight to attack with utter ferocity. Death Knights still use the code of honor they held in life (never attacking from behind for example) and retains all of its fighting skills. They will never surrender and will only parley if their opponent possesses something they want (such as knowledge of the fate of a former family member).

Abilities
In D&D 3e, a death knight has a number of spell-like abilities:
 * It can use either Power Word Blind, Power Word Kill or Power Word Stun once a day.
 * It continuously radiates Fear in a 5 foot radius.
 * It can cast Detect Magic, Detect Invisibility and Wall of Ice at will.
 * It can cast Symbol of Pain or Symbol of Fear once a day.
 * It can cast a 20HD Fireball once per day.
 * It has an 80% chance of wielding a magical sword, which has a 1 in 6 chance of being one of the following: Long Sword +2, Two-handed Sword +3, Two-handed Sword +4, Short Sword of Quickness, Short Sword of Dancing, Short Sword of Life Stealing. (This last ability is from 2nd edition DnD, so it may not apply now.)

The most famous of all death knights is Krynn's Lord Soth, cursed after he murdered his wife to continue an affair with an elfmaid.