Nerull's Curse
From Davenrathh
One of the most powerful items in the entire world of Terradon, Nerull's Curse was more than just an artifact. Many believe that it was the Breath of Nerull, the God of Death, shaped into a vessel to be used as a weapon. The Magical equivalent of a high-yield nuke, Nerull's Curse had enough power to destroy most of Aberdon. When it was activated by Ian Mosswilde following the death of his father Mosslaide, it blasted a hole fifty miles wide in the centre of the continent. Some suggest that the blast was so powerful that it could not be contained in one time or place, which explains why Aberdon was wracked for months aferward by many subsequent explosions.
The effects of the Curse were felt for generation's afterward. The massive energy of the blast tore a hole in the dimensional fabric, allowing many demons and monsters from other planes to slip into Aberdon. Worse, the dark energies associated with Nerull saturated the land, causing the dead to rise with greater frequency, and hightened power.
The effects of the Curse have slowly come to abate, perhaps in part to the defeat of Aberdon's Tyrant Cromwell at the hands of Meldorian, Uther, Airtheus and Dalanar. The dimensional rift was eventually penetrated and sealed by two of Aberdon's most powerful heroes, the priest Braden and the archmage Althamus.