Death Knights

"Death Knight" is a series of cards that include "Death Knight" in their card name exclusive to the Extinction Force clan. The first card was introduced in Booster Set 00: Jack of All Trades and gained further support in Extra Booster 00: Legion of the Damned. Their grade 0, 1, and 2 units revolve around calling to open rearguard circles from the drop zone and sending to the soul to fuel the grade 3 and 4 units that utilize powerful Soul Blast abilities that call units to filled rearguards as well as open to refuel the field for more attacks.

Booster Sets

 * Booster Set 00: Jack of All Trades

Extra Boosters

 * Extra Booster 00: Legion of the Damned

Background
What are the "Death Knights"?

The Death Knights are the elite army of the Great King of Cocytus, a land in Dimension X that has led a rebellion against both the Gods and Zachary for over three centuries. After attaining power over death during a battle with Zachary, Erebus raised some of his and his enemies' best warriors from the dead and shaped them into his weapons. Casting aside their old names, these Death Knights have taken up the mantle of the 72 Pillars, the names of the 72 demons that once waged the greatest war in history against the Gods.

The Cray Wars

After arriving on Cray during the Sundering, Erebus, along with his most trusted knights, ventured into the Dark Zone, where they encountered Zachary fighting against the forces of the Pale Moon Circus. Together, the Death Knights entered the fray and cut down many of Zachary's and Luquier's forces. By the end of the battle, the Death Knights had retreated, leaving no evidence of their involvement other than a trail of fallen warriors.

Grade 0

 * Herald of Death Knights, Valefor (Undead)
 * Inquisition Death Knight, Flauros (Draw) (Undead)
 * Nefarious Death Knight, Amy (Heal) (Undead)
 * Reprobate Death Knight, Zagan (Stand) (Undead)
 * Vile Death Knight, Seere (Critical) (Undead)

Grade 1

 * Death Knight of Decay, Forcas (Abomination)
 * Fiendish Death Knight, Sitri (Undead)
 * Immoral Death Knight, Crocell (Undead)
 * Malicious Death Knight, Ronove (Undead)
 * Sinful Death Knight, Sallos (Undead)
 * Sinister Death Knight, Cimeries (Undead)

Grade 2

 * Death Knight of Disease, Valac (Abomination)
 * Diabolical Death Knight, Oriax (Undead)
 * Execrable Death Knight, Murmur (Undead)
 * Heinous Death Knight, Andras (Undead)
 * Malefic Death Knight, Stolas (Undead)
 * Trumpeter of Death Knights, Ipos (Angel)

Grade 3

 * Lord of Death Knights, Gremory (Undead)
 * Deleterious Death Knight, Marax (Undead)
 * General of Death Knights, Gamigin (Undead)
 * Pernicious Death Knight, Gusion (Undead)
 * Vindictive Death Knight, Agares (Undead)

Grade 4

 * Atrocious Death Knight, Focalor (Undead)
 * Calamitous Death Knight, Phenex (Undead)
 * Satan of Death Knights, Erebus (Lich)

Gate Card

 * Jigunna, Hall of Death Knights