In actual fact, Frostmourne's story has been linked to WOTLK Classic Gold several Lich Kings in Warcraft's history including, but not only along with Arthas Menethil.

After defeating Ner'zhul Frostmourne was found by Arthas Menethil. Enticed by the strength that was Frostmourne, Arthas took the sword and became an undisputed Lich King.

It was among the greatest tragedies in Warcraft and it has consequences that persist today. as the current Lich King Arthas was able to use Frostmourne to commit a variety of atrocities to its own citizens.

After more than a decade after Wrath of the Lich King was released, Frostmourne is most closely associated with Arthas Menethil.

Once Arthas had been defeated during WoW: Wrath of the Lich King by Tirion Fordring, Frostmourne was shattered. The souls inside were liberated, and fragments were then presumably disposed of for safe-keeping (although it's never explicitly said who was the one to have the shards).

Frostmourne's hilt eventually was placed at a statue erected in honour of Tirion Fordring. In Legion, however the shards were rebuilt into two runeblades that were more powerful: Icebringer and Frostreaper.

These blades were later referred to as The Blades of the Fallen Prince, alluding to buy WOW WOTLK Classic Gold Arthas Menethil's disappearance from the limelight.