If you see some unique items not appearing on item lists, but the templates appear to be working correctly please perform a null-edit (log-in into gamepedia, press "edit" button, save the page without any changes). First do it on the unique page and then on the list page.
List of unique monsters
Unique Monsters are special monsters with fixed modifiers that appear always in the same zone.
Listed below are only the unique monsters that are part of the main storyline. Map bosses, Invasion Bosses, Corrupted Area bosses, summoned monsters during Izaro fights, Beyond Demons, Tormented Spirits and Rogue Exiles also have a rarity of unique, but are not featured in this list.