Sometimes a map has a randomly placed event item in it which could be collected to purchase items in one of the four shops in the event map. Once collected on the maps, event items will appear on your back and won't be obtained until you bring the cheese to the hole. You can spend these currencies on the event map in the shop listed below.
Five seconds has to pass before you can collect the event item on a map. If you are revived by a shaman using the Ambulanceskill after collecting an event item, you will still have the item when you respawn, negating the need to collect it again, despite the fact it no longer appears on your back.