The Orb of Ner'zhul was a powerful artifact of the Scourge. Wielded by the ghoul Ichor, it had the power to raise undead beasts such as Frost Wyrms and Ancient behemoth, and enabled the bearer to command them. The Orb was taken by the Forsaken Baron Valimar Mordis, who intended to use its powers to raise his own army of undead. His own power alone was insufficient to raise more than a single frost wyrm, so he tricked Anveena Teague - the avatar of the Sunwell - into aiding him, using her power to augment that of the Orb.
The Baron's bodyguard and friend, the tauren Trag Highmountain, realized what the Baron intended, and confronted the Forsaken nobleman as he raised undead behemoths to do his bidding. Trag closed his fist around the Orb in the Baron's hand, destroying it, and causing the frost wyrm the Baron had summoned to crash onto the castle. Though the crash killed Trag, the power of Orb caused him to rise again as an undead.