Lor'themar Theron is the Regent Lord of Quel'Thalas, and was the leader of the blood elves of Azeroth in the absence of Prince Kael'thas Sunstrider. After Kael'thas' betrayal and eventual death, Lor'themar has become the sole leader of his people and seeks to lead them to a brighter future.
In the Second War, Lor'themar was second-in-command to Sylvanas Windrunner, Ranger-General of Silvermoon, he defended Quel'Thalas against the invasion of the Horde, then he accompanied Turalyon and the Alliance forces to Capital City and helped them to defend themselves against the orcish threat.
Many years later the traitorous Prince Arthas, having already ravaged his own homeland, the Kingdom of Lordaeron, led the undead Scourge against the high elves. The Ranger Corps fought Arthas at every turn but were pushed further and further back towards their capital. Sylvanas Windrunner was slain by Arthas outside Silvermoon, the city was sacked, and King Anasterian and the entire Convocation of Silvermoon were killed battling the invading undead. After Sylvanas' death, Lor'themar assumed temporary leadership of the high elves and, along with his much-reduced forces, remained in Quel'Thalas after the fall of Silvermoon as a resistance to the Scourge remnants.
Not long afterwards, Prince Kael'thas returned from Dalaran to proclaim the rebirth of the former high elves as the blood elves, or sin'dorei, in honor of their fallen brethren. Chosen as Regent of Quel'Thalas, Lor'themar was commanded to "safeguard the land and seek a cure for their people" while Kael'thas took a group of the blood elf forces to join the Alliance resistance against the Scourge in Lordaeron, led by Lord Garithos. His old friend Halduron Brightwing, Ranger-General of Silvermoon, aided him in this task.
Lor'themar Theron has promised to lead his people to Glory after the betrayel of Kael'Thas