"Not even the mighty Sapphiron was safe from Frostmourne's bite. This wise blue dragon was a master of arcane magic and one of the greatest of his kind who had ever lived. For many ages, he and his loyal draconic servants stood guard over a trove of extraordinary relics in Northrend.
It was these relics that drew Arthas's attention to Sapphiron. The death knight and his Scourge minions invaded the dragon's lair to pilfer its treasures. The battle that followed would become one of legend.
Sapphiron and his fellow dragons unleashed the full fury of their arcane might on Arthas, but he would not be denied his prize. The death knight overwhelmed his ancient foes and slew them one by one. Calling on Frostmourne's powers, Arthas then transformed Sapphiron into an undead frost wyrm."
"Lady Jaina Proudmoore is the most powerful human sorceress alive
<Jaina is still catching her breath.>
I can barely believe we're still alive"
King Anasterian Sunstrider (killed on the Isle of Quel'Danas, Arthas: Rise of the Lich King)
Antonidas (killed in Dalaran, Warcraft III)
Kael'thas Sunstrider
illidan stormrage
and many others
Chris Metzen replied: "Arthas and Ner'zhul have become a perfect fusion of one being - Arthas' personality and body with Ner'zhul's wisdom, experience, power and EVIL."
"A debate that has arisen among fans is whether the Lich King can be classified as a god. His origins lie with Kil'jaeden, but his power has continued to increase at an exponential rate beyond Kil'jaeden's intentions."
"Darion Mograine: You are dealing with a being that holds within it the consciousness of the most cunning, intelligent, and ruthless individuals to ever live.
Darion Mograine: The Lich King is unlike any foe that you have ever faced"