Matthias Lehner

Matthias Lehner is a ghostly child, who appears in several locations in Icecrown, offering several quests related to the Lich King depending on his location.

The Heart of Arthas
Matthias Lehner (an anagram of Arthas Menethil) first appears when the player finds a strange object far beneath Icecrown Citadel. Matthias Lehner then shows the player seminal events in the life of Arthas Menethil: the slaughtering of his own soldiers after taking up Frostmourne, the raising of Sindragosa, and the battle between Arthas and Illidan Stormrage.

It is eventually revealed that the strange object is the frozen heart of Arthas. When this information is presented to Tirion Fordring, he believes the heart can be used to help redeem Arthas and thus defeat the Lich King. Tirion Fordring infiltrates the ceremony, held in the Cathedral of Darkness, where the heart is to be destroyed, along with a cadre of his knights. Unexpectedly, the Lich King arrives at the ceremony and immediately identifies Tirion through his disguise. The Lich King beckons Tirion to stare into the frozen heart. Tirion decides that there is no chance to redeem Arthas, and destroys the heart himself. This process nearly kills Tirion, and drastically weakens the Lich King. Before the Lich King's minions can overwhelm Tirion, the Knights of the Ebon Blade arrive led by Darion Mograine himself. They subdue the Lich King's minions and flee with Tirion before they suffer the Lich King's wrath.

Quests
The chain that eventually opens Matthias' quests begins with Exploiting an Opening / Opportunity (quest).


 * Army of the Damned
 * Do Your Worst
 * Futility
 * A Voice in the Dark
 * Return to the Surface
 * Time to Hide
 * Time for Answers
 * Where Dragons Fell
 * Knowledge is a Terrible Burden
 * The Hunter and the Prince

Speculation

 * Not much is known about Matthias. It is speculated by some that he is the embodiment of the last piece of Arthas' humanity, which was banished when the Prince took to the Frozen Throne and became the Lich King, the name "Matthias Lehner" being an anagram for "Arthas Menethil." This theory gains support in Arthas: Rise of the Lich King where an unnamed blond-haired boy exists in Arthas' mind, urging him to reject Ner'zhul's influence. This theory is further acknowledged in Edge of Night, when Sylvanas sees Arthas as a little blond boy forever tormented in the afterlife of shadows.
 * Sean Copeland implied that Matthias' appearance in the game may have been only for gameplay reasons.
 * The boy from Arthas: Rise of the Lich King was not written as Matthias Lehner. Rather, a quest designer made a character based on the boy without Christie Golden's knowledge that was very likely intended to be the same character. This explains the disconnect in the character's "death" and reappearance.
 * Another theory supposes that he may be an illusion of Yogg-Saron or some other entity, whose intent is to cause harm to the Lich King by convincing players to destroy his heart. This theory is mostly based on the fact that he encourages players to gather friends when they are going after the heart during the quest Knowledge is a Terrible Burden.