What is the Wrathgate Event in World of Warcraft

The Wrath Gate is the central gate leading into Icecrown, and one of the greatest barriers to prevent an invasion from the Horde and Alliance. It is guarded by many undead beings, including giant frost Vrykul and Abominations.

During the assault on the Wrath Gate, Saurfang the Younger and Bolvar Fordragon joined hands to assault the gates, gauding the Lich King into appearing before them. When he did, Saurfang assaulted him but was slain and his soul taken by the Lich King.

His triumph lasted short, however, as a contingent of Forsaken under command of the Grand Apothecarist Putress bombarded the Scourge, Horde and Alliance forces with barrels of a plague so virulent, it harmed even the Lich King. As hundreds lay dying, including Bolvar, the Red Dragonflight swooped in, and burned all to ashes to prevent them from rising as a new form of undead.

The Wrathgates would remain closed, the Alliance and the Horde back at each others' throats.

An investigation led by Thrall on one end, and Varian Wrynn on the other, led to the conclusion that Putress had masterminded this assault under command of the Dreadlord Varimathras and had now laid claim to Undercity.

Assaults were made that ended the duplicity of Putress and ended the life (presumably) of Varimathras, leading to the Undercity once again being under the control of Sylvanas. However, the breach of trust between Horde and Alliance would not be so easily mended again.

The plot thickens, as the corpses of neither Bolvar nor Saurfang were recovered...