Lothar was the Guardian of Thraben and was personally in charge of the defense of the Helvault. He also discovered and mentored a young cathar by the name of Thalia who would succeed him as the Guardian of Thraben.
Thalia, a second-year cathar, attracted the attention Lothar, a revered soldier who led a force of elite protectors in service of the Lunarch when he witnessed Thalia charging into an entire howlpack of Krallenhorde werewolves to rescue a single old man, and was impressed with her selfless valor. The young cathar slashed and fought and risked everything for a single innocent soul, and Lothar made her part of his elite guardians that very day. Soon, she rose to become Lothar's second in command, entrusted to help him defend the High City of Thraben.
As Lothar's trusted right hand, Thalia learned of the Helvault, the great silver obelisk in the Cathedral courtyard. Lothar taught her that the Helvault was a protected holy relic of the Avacynian Church, but she was not told the secret: that the missing archangel Avacyn had become imprisoned within it as not even Lothar himself knew this.
When Geralf and Gisa led their army of undead against Thraben Lothar went missing forcing Thalia to lead the city‘s defenses. Plagued by strange, evil voices during the battle, Lothar had plunged off one of Thraben's high walls to his death.
His body was discovered and recovered after the siege and his title as Guardian of Thraben was passed to his second in command by the Lunarch Mikaeus.