Players may occasionally succeed in creating rare, [[supreme item|supreme]] or even [[fantastic item|fantastic]] items. These tools are faster, weapons do more damage, and armour protects a bit better. This may also happen as you improve or polish items and rare items may turn into even rarer items. Constructing new items using rare materials may turn the unfinished item into a rare item. Rare guard towers spawn more guards, for instance. More functionality will be added over time.
If you have the Weather sounds turned on, Generally you should generally hear a "drum-roll" when a chance of creating a rare comes up. (Fishing is one exception to this; there may be others)
When rares were introduced, we were told "You get approximately 1 chance of 50% each hour to create a rare item." What this actually means to game play is unknown. The odds of creating a rare seem to be much higher than improving an item and making it rare.