The Skull of Gul'dan

The Skull of Gul'dan was a powerful demonic artifact created from the skull of the orc sorcerer Gul'dan. Used for a plethora of demonic activity, from opening portals to corrupting the northern forests of Ashenvale, its powers were finally consumed by Illidan Stormrage. Although already consumed by Illidan, the skull still holds power and is in Illidan's possession.

History


After the insidious warlock Gul'dan died, his skull was turned into a channeling totem for demonic energy. It was briefly held by a low-ranking Bonechewer warrior before it was claimed by Hurkan Skullsplinter, the Bonechewer chieftain. Not realizing its power, the orc wore the skull as a symbol of his station, before he was killed by Grom Hellscream. The skull was acquired by Ner'zhul for use in opening portals to other worlds, which also required the Book of Medivh, the Eye of Dalaran, and the Jeweled Scepter of Sargeras.

It turned out that the skull wasn't really needed to rebuild the Dark Portal, but Ner'zhul kept it as a trophy of his triumph over his apprentice. The skull appeared to hold some shard of Gul'dan's soul within, enabling the dead warlock to communicate with Ner'zhul. Deathwing later demanded it as payment for his services for purposes unknown. Additionally, it is implied several times that the Skull has corrupting properties on its wielder as the voice of Gul'dan slowly tempts him over time.

Khadgar, Alleria Windrunner, and Turalyon managed to steal the skull and the Book of Medivh from Ner'zhul well into the Alliance Expedition's campaign. Khadgar used the skull and the Book of Medivh to close the Dark Portal, and sent both artifacts back to Azeroth via gryphon rider, but wasn't certain if they completed the transit.

Reign of Chaos
Years later it would appear again on Azeroth, this time used by the Burning Legion to corrupt the forests of Felwood. The skull's powers were eventually consumed by Illidan Stormrage who, upon absorbing its power, became half night elf and half demon. With his newfound power, he struck a major blow to the Legion by killing Tichondrius. Illidan retained memories of the Tomb of Sargeras from Gul'dan, which he used in tandem with his own knowledge of Suramar to find the Eye of Sargeras.

''Exactly how the Legion regained the Skull is unknown. Beyond the Dark Portal establishes that Khadgar intended for it to return to Azeroth, but it is vague as to what happened. The fact that Gul'dan's spirit lingered on within the Skull was long speculated by some, and this feature may explain some of Illidan's behavior.''

The Burning Crusade


When Illidan "consumed" the skull it was not destroyed, and Illidan kept it in his possession. The opening cinematic of the Burning Crusade features him holding the skull in his claws, and he can be seen in-game doing the same thing. The skull is now part of Illidan's loot table.

Powers
In Warcraft III: Reign of Chaos, consuming The Skull of Gul'dan doubled Illidan's base attack damage (from 34-56 to 75-123) and allowed him to deal chaos damage, which was fully effective against all types of armor (including the Divine Armor of Tichondrius). In addition, it metamorphosed Illidan in a powerful demon with ranged attack. It also increased Illidan's strength, agility and intelligence which resulted in his health points increasing by 300 and his mana points by 90.