Event effects appear at locations together with the main game modes or anomalies during game events.
During an Event, additional items not included in the search list appear at the event location. Collect these items to have them credited to you as event currency (for more details, see "How do I earn Event Currency?"). Secret items may also appear at additional themed locations (for example, Christmas locations).
They appear at some locations during Phantom Hunt-style events. One of the items on the search list becomes a phantom and is shown in a different color. When you find the phantom, a different name on the list gets highlighted in color. You need to find as many phantoms as possible at the location.