As of the December 3rd update (2020), the Chaos Invasion now has different levels the player can set at the start of campaign. These are "On" "Off" "Hard" "Very Hard" and "Legendary". This scales the number of armies spawned during the Chaos Invasion.
The Old World despairs, for Archaon the Everchosen, Champion of Chaos, has come and with him the End Times!
Once a Templar Priest of Sigmar, Archaon uncovered a terrible secret which drove him to reject his faith and pledge himself to the Gods of Chaos. In their service, he has devoted himself to the world's destruction, defeating all challengers and rising to a position of dominance over all in the Chaos Wastes, achieving the ultimate accolade - his dark coronation as the Everchosen; the vessel through which the Dark Gods unite their followers to turn the world into a Realm of Chaos. It is to his banner that the Warriors of Chaos have been flocking, and it is his malign will that now drives them forth in a terrible wave of destruction destined to sweep all before it.
The earth groans beneath the iron-shod feet of Archaon's numberless horde, and with him comes death. Is there any champion of the Old World mighty enough to withstand the Lord of the End Times?
The invasion can be very destructive. The factions who attack are mostly hordes or similar factions, so they tend to raze a lot of settlements. Additionally, there is a global +2 Chaos Corruption during the invasion.
Factions involved in the invasion:
- Warriors of Chaos are the primary aggressors. In Mortal Empire, these subfactions used to be included but have been removed:
Opposing Chaos is The Empire, Dwarfs, Bretonnia and other human factions. In Mortal Empires, they are joined by High Elves and Lizardmen. These factions gain the diplomatic trait Shield of Civilization during a Chaos Invasion, making them more likely to stick together against Chaos.
Greenskins, Vampire Counts, Skaven, Dark Elves and Tomb Kings do not gain this trait, though they are automatically at war with the Warriors of Chaos, who will not hesitate to attack them if they get in the way.
Wood Elves will also automatically be at war with the Warriors of Chaos, in addition to having negative diplomatic relations with other Chaos factions, especially Beastmen whom they hate.
Many factions have a campaign victory condition that involves wounding Archaon and dealing with the Warriors of Chaos.
What happens if I'm playing as the Warriors of Chaos, Norsca, or Beastmen?
If you are playing as a Norscan faction (World Walkers or Wintertooth), you will get an event called The Everchosen's Summons which allows them to choose to side with Archaon and the Warriors of Chaos, or to side against them and bring about your own invasion.
If you are playing the Warriors of Chaos themselves, you will get an event called The Treachery of Tzeentch; you will still have to fight a rival faction called Chaos Gathering, led by Sarthorael the Everwatcher. In addition, Varg and Skaeling will not automatically be your vassals, but you have the ability to Awaken the Tribes to call addition Norscan Tribes to the map.
If you are playing as any Beastmen tribe, you are not at all summoned to join the Everchosen in his conquest. However, the warriors of chaos will not start at war with you. You can choose to aid them and continue your own campaign. You have the option to go to war with them, but there is no real gain from doing this. It is suggested to leave them be and continue your own campaign, potentially helping them if you desire.
How it plays out
- The Chaos Stirs notification indicates the impending arrival of Warriors of Chaos armies.
- The The Rise of Chaos notification indicates the initial spawning of Warriors of Chaos armies in the Chaos Wastes. On Normal, four full Warriors of Chaos army stacks will spawn in the northeast corner of the map and attack the nearest factions.
- The The Doom Tide notification indicates the additional spawning of Warriors of Chaos armies. It occurs after the first Chaos wave is defeated.
- The Chaos Invasion begins in earnest when Archaon spawns alongside Kholek, Sigvald, Sarthorael and additional Chaos armies. As of the December 3rd update (2020) this will take place between turns 140 and 160. On normal difficulty and in Mortal Empires, these armies consist of the following full stacks (selecting Hard increases these numbers by 50%):
- Old World: nine Warrior of Chaos and two Warherd of Chaos stacks in the northeast.
- New World: six Warrior of Chaos stacks in the north.
- Southlands: three Warherd of Chaos and two Warrior of Chaos stacks in the southeast.
- When Archaon and the Warriors of Chaos are finally defeated for good, the invasion is over.