Invincible was born to the mare Brightmane on the Balnir Farmstead in Tirisfal Glades, in the winter of the year Stormwind fell. Prince Arthas, then nine years old, was present when he was born, and was given the horse by the Balnir family, who bred horses used by the royal family. The horse had a white coat, different from the usual Balnir stock, which normally had gray coats. Arthas had considered naming the horse "Snowfall" or "Starlight", but in the informal tradition of Lordaeron knights and nobles naming their steeds after a quality (Uther's was "Steadfast", King Terenas' "Courageous"), he named the colt "Invincible".
Ten years later in winter, before Arthas was inducted into the Knights of the Silver Hand, Arthas and Invincible were caught in a sudden blizzard while en route to Balnir Farmstead. When Arthas came to a jump that Invincible regularly made, the horse lost its footing on the ice, propelling the young prince and his mount into rough terrain. Arthas blacked out for mere moments, but his steed was laying in the bloody snow with two broken front legs. Too far from help and unable to heal the wounded horse, Arthas forced himself to drive his sword through the beast's heart in order to relieve his pain. After the storm tapered off, Jorum and Jarim Balnir found the young prince curled up next to his once majestic mount. Stricken by a mix of guilt and pride, Arthas didn't tell anyone that it was a completely unnecessary jump that lead to the accident. He was buried on the grounds of the Balnir Farmstead at Arthas' request. Invincible's death was one of the events that inspired Arthas to become a paladin.
After the fall of Lordaeron years later, Arthas - now a death knight - ran directly from Lordaeron after murdering his father, to the Balnir Farmstead where Invincible was buried. With the power of Frostmourne, Arthas resurrected the horse as his undead steed. Now fully living up to his name, Invincible could become a spectre and disappear, to be resummoned by Arthas at any time.
During the Scourge's siege on the Sunwell, Anasterian Sunstrider confronted Arthas in single combat, severing Invincible's forelegs with his runeblade, Felo'melorn, to dismount him. Witnessing Invincible's injuries brought on a surge of memories and sent Arthas into a rage, during which he shattered Felo'melorn and struck down Anasterian. This time, however, Arthas was able to necromantically repair the injuries. It is likely that Invincible still serves as his master's steed, even after Arthas became the new Lich King, though Sindragosa has also been referred to as his mount.
In World of Warcraft
This section concerns content exclusive to World of Warcraft.
Beloved steed of Prince Arthas Menethil
Loyal and great of heart in life, may you find peace in death.
Pure streams and green pastures, devoted friend.
The open grave was introduced in Patch 3.0.2, Echoes of Doom, but went unnoticed until just before the Zombie Infestation phase of the Scourge Invasion, which heralded the release of World of Warcraft: Wrath of the Lich King. However, Arthas: Rise of the Lich King indicates that the grave had already been open for several years.
In Wrath of the Lich King
This section concerns content exclusive to Wrath of the Lich King.
On January 22, 2010 a music piece titled "Invincible" was released on the WoW 5 Years Anniversary Battlecry Mosaic:
- "An ode to one who has fallen. Time and events have left it unclear whether the song refers to the former prince of Lordaeron or his beloved steed."
The song largely revolves around a recurring lyrical leitmotif, "An Karanir Thanagor, Mor Ok Angalor. Mor Ok Gorum Palahm Raval" which can also be heard in the closing cinematic of Warcraft III: The Frozen Throne and in the opening cinematic of World of Warcraft: Wrath of the Lich King.