An alliance of most of the Duergar kings united under the rule of High King Darmond Phragos the Great, several Drow Houses from the Underdark, Kobold king Rovni, a handful of Goliath and Orc tribes and the Goblin tribe of Goblin king Ragos the Enraged begin their assault on the overworld. The hundred year-war eventually causes the fall of the Kingdom of Varadaral, marking the end of the War of Phragos and the Fifth Age.
The War of Phragos mostly rages in the Kingdom of Varadaral, but also outside of it, the alliance of Phragos rages against the overworld, primarily in the Kingdom of Tessuris. Disguised as (Deep) Gnomes, the inspire race riots in Strolis and Dol Felmor and eventually begin their open assaults against both cities simultaneously. This ensures that the alliance between the county and duchy finally breaks.
The alliance between the Duergar, Drow, Kobolds, Goliath, Orcs, and Goblins lasts for some time, but eventually breaks apart: King Rovni and King Ragos the Enraged fight as often against each other as they do against those of the overworld and their forces are quickly rendered ineffective some 20 years into the war. The Goliath and Orcs remain loyal for most of the war, but are eventually exhausted. The Drow Houses eventually betray High King Darmond Phragos the Great on the Darkest Night , but this is not enough to prevent the collapse of the Kingdom of Varadaral. It does however ensure that the Duergar Alliance breaks soon after, but it still takes nearly 20 years after the end of the war that the last Duergar king is killed and his troops driven back underground.