Arthas raises Sapphiron as a frost wyrm

Full History

Arthas defeated the dragon Sapphiron during his campaign in Northrend and raised the creature into undead service as a frost wyrm. The transformation gave the Scourge another terrible aerial weapon as the death knight hurried toward the threatened Frozen Throne. It also showed the extent of necromantic domination over creatures once powerful in life.

Sapphiron belonged to the dragon kind whose history had long been entangled with the defense of Azeroth. Arthas approached the encounter as a servant of the Lich King, for whom the death of an enemy could be made to supply another soldier. Raising the dragon changed the meaning of victory: the defeated creature's strength did not disappear, but was stolen for the undead army. Northrend's dangers thus became resources for the very power seeking to rule it.

The event belongs to Warcraft III: The Frozen Throne, before the later stories told about Sapphiron in the World of Warcraft raid era. It is important to the march on Icecrown because it demonstrates how Arthas increased his strength while his master's peril grew. The fallen dragon's service is an emblem of the Scourge's ability to turn loss into further terror.