Game concept · The Northern Lords
Varangian Adventure
The game also links it as Varangian Adventures, Adventuring, Adventure.
From the game's encyclopedia
This is a special type of War, where the attacker intends to move their Realm to the War Target wholesale.
If they win, they will immediately annex the appropriate Counties and move their Capital there. Their old vassals will go independent, and their old Counties will be given to upstart local warlords. Varangian Adventures are ONLY available to Duke and Count-Tier Rulers, becoming progressively more expensive with each successful Adventure.
This Casus Belli is NEVER available after the Tribal Era, and cannot be used against other Cultures that can Adventure or against neighboring Rulers.
North Germanics launching their first Varangian Adventure receive up to 2000 bonus Special Soldiers, the amount going up with every same-Faith same-Culture county they completely control within Mainland Scandinavia.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Varangian Adventure is an entry of Crusader Kings III's in-game encyclopedia (The Northern Lords). The game explains it: "This is a special type of War, where the attacker intends to move their Realm to the War Target wholesale." The game also links it as Varangian Adventures, Adventuring and Adventure. Patch 1.20.1.2, from game/common/game_concepts/01_fp1_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/01_fp1_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.