Minecraft wiki entry for Advancement_guide, associated text: First, kill a raid captain (which will award the "Voluntary Exile" advancement) and get the Bad Omen effect. Then, go to a village. You will see a bossbar labeled "Raid" and your Bad Omen effect disappeared, indicating that the raid has started. There will be numerous amounts of waves of the raid based on the difficulty. There are 3 waves in Easy, 5 in Normal, and 7 in Hard.