Grand Inqusitor Isillien was a villain from the World of Warcraft MMORPG. He was the spiritual leader of the Scarlet Crusade, and was based out of the Western Plaguelands at Mardenholde Keep. He has since been removed from World of Warcraft due to his death.
The priest Isillien was formerly a priest of the Holy Light in Lordaeron, assigned to be the liaison for the Knights of the Silver Hand. There he worked closely with the elder High General Abbendis and his youthful charges, tutoring the young paladins in their quest for truth. He fled with Abbendis as Lordaeron fell to the Scourge. Priests and paladins fought as the Scourge attacked the city, but they fled as Lordaeron fell around them. Some whisper it was the wounds both men received in battle, or perhaps just the shock of seeing their whole purpose destroyed, but since that day both Isillien and Abbendis have been quite insane.
Isillien and Abbendis wandered the area as the Scourge defiled the land, destroying what undead they could, gathering what warriors would join them. They had but one concern: eradication of all that had destroyed Lordaeron. Isillien became the spokesman for the group, his ravings gaining more followers than repelling them. Isillien is the heart of the Crusade. Abbendis and Isillien felt that although they had a good base, they really needed to attack the Scourge where they were the thickest: in the Eastern Plaguelands. Isillien took on the title of Grand Inquisitor and control of the Western Crusade, while Abbendis led the majority of the forces to Tyr’s Hand in the east to strike at Stratholme. Isillien guides the priests in the Crusade in their new roles as inquisitors, based in the Western Plaguelands. He is in charge of questioning undead and mortals alike to ferret out whatever information he can on the movement and settlement of the undead. Isillien controls the warriors through his impressionable paladin Taelan in the west. Isillien taught Taelan Fordring about the Holy Light and what it was to serve.
When the Scarlet Crusade was founded, Isillien realized that the order would be forced to deal with living adversaries as well as undead. Sadly, most spells focused toward either harming one or the other — a difficulty he was determined to resolve. Isillien developed a series of variations on healing spells that would not only inflict harm upon the undead, but on living victims as well. He passed this teaching on to each potential inquisitor, and it has become one of their trademark abilities.
During a meeting of members of the Knights of the Silver Hand in Southshore, he tried to destroy the dark crystal then-Commander Mograine had recovered after the Battle of Blackrock Mountain with Smite - only to find out it absorbed the Light. This discovery led to the creation of the Ashbringer.
Isillien continued to lead the Scarlet Crusade until several months prior to the War in Northrend. Tirion Fordring, living in exile in the Eastern Plaguelands since he was accused of treason by the Alliance, enlists adventurers to help redeem Taelan. When they succeed, Isillien confronts Taelan, claiming to be dissappointed in him, then killing him. Tirion arrives on the scene and kills Isillien in a murderous rage, then he reforms the Order of the Silver Hand. Isillien's death heralded the shattering of the power structure of the Scarlet Crusade in the Eastern Kingdoms, and by the time of the Fall of the Scarlet Enclave, Brigitte Abbendis, who had assumed the title of High General after the death of her father, was the only remaining leader of the Scarlet Crusade. When the Scourge decimated the Scarlet Enclave, Abbendis disbanded the Crusade and reformed it as the Scarlet Onslaught. The Crusade's remaining holdings were claimed by the Argent Crusade, while the Crusade's remnants either went into hiding or fled into Tirisfal Glades.
Once a devoted priest of the Holy Light, he now sees his dedication to the Crusade as an even greater purpose. This dedication is real; it’s a powerful and total commitment to something that has measurable results — something the Holy Light never gave. Early in the life of the Crusade, he developed techniques for inquisition and questioning, as well as holding cells and torture chambers to extract information or to hold prisoners or initiates to see if they are infected by the plague. Undead are also held in these cells, and Isillien often visits them late at night, always alone. Crusaders say he enters the dungeon looking angry and almost mad (“mad” relative to the average crusader, which would be justifiably insane to the average eye). He exits calm and smiling, and speaks to no one about what he has been doing, and no one cares enough about the undead to wonder too much.