Abyssal Plague

The Abyssal Plague is a worlds spanning event created by Wizards of the Coast. The novels come from the Dungeons and Dragons, D&D: Forgotten Realms, and D&D: Dark Sun campaign settings. Starting with a five-part novella (The Gates of Madness). The insidious plague also reaches into roleplaying products such as Monster Vault: Threats to the Nentir Vale and future seasons of D&D Encounters.

"In a dark dimension beyond the known planes of existence, the Chained God thirsts for freedom. Infusing his will into the residue of a long-dead universe—scarlet liquid shot through with veins of silver and flecks of gold—he sends this liquid crystal between worlds to prepare his way. But his will is not the only force that drives the Voidharrow.

Imbued with the power of the Voidharrow, the dragon Vestapalk creates a horde of demonic minions to spread the Abyssal Plague across the Nentir Vale. But the threat is not contained within a single world: Faerûn and Athas must contend with their own outbreaks of tainted demons and virulent plague. Will the Voidharrow consume the multiverse? Will the Chained God break free? Or will the heroes of the age put a stop to the Abyssal Plague?"

Books in the series
Follow up with Sword of the Gods by reading Sword of the Gods: Spinner of Lies. (Part of the Rise of the Underdark event)

Before reading Shadowbane, consider checking out Downshadow (novel) (Part of the Waterdeep (series)) and then after Shadowbane, follow up by reading Shadowbane: Eye of Justice.