Warhammer 40,000 (2017), p167 — War in the Rift

Ever jealous of one another, the Dark Gods began to war amongst themselves in realspace. The opening campaign saw Tzeentch and Khorne send legions to the Scourge Stars seeking to destroy Nurgle's growing foothold. War spread as Nurgle recalled his lieutenants from Ultramar and counter-attacked the realspace strongholds of his rivals. Slaanesh allied with all sides at different times, always furthering his own gains. The greatest of Daemons met in grinding clashes of attrition at the titanic Battle of Vigrid, the fighting only ending when all agreed to Tzeentch's proposal to settle the war via a contest of champions.