The advancement minecraft:adventure/kill_all_mobs requires you to kill a Illusion Illager and they do not spawn so it is impossible to get the advancement minecraft:adventure/kill_all_mobs in survival mode
The advancement minecraft:adventure/kill_all_mobs requires you to kill a Illusion Illager and they do not spawn so it is impossible to get the advancement minecraft:adventure/kill_all_mobs in survival mode
(Unassigned)
Confirmed
advancement, illusion_illager, kill
Minecraft 17w17b
Minecraft 17w18b
Retrieved
Could it just be that they don't spawn yet and they are holding off until full release to show that feature?