From EpicDuel Wiki

The Rarity of an item shows it's availability. Certain items in the EpicDuel world are difficult to come by as they are offered in limited quantities or for limited durations.

EpicDuel currently offers four types of rare items:

• Limited Rare: These items are offered with fixed quantities at particular merchants. When the quantities run out, these items are no longer available
• Seasonal Rare: These items are offered once annually during a particular time period. See Category:Events for recurring in-game events.
• Rare: These items are offered as exclusive items that will never be released again. Rare items are very valuable in that they can not be obtained at any point in the future
• Ultra Rare: These special items are offered for short periods of time, are extremely powerful, and contribute greatly to the overall rarity score of the player.
  
  

Rarity Score

Every rare item has a rarity score. The rarity score of each item in your inventory is summed to give your character's Rarity Score. Rarity Scores can be appraised by Charfade, Naomi, Junker, Zedmyr, Cinderella, Snork, The Lawman and Slayer for 500 Credits. Having a character Rarity Score of 25000 or more will award you the Treasure Hunter achievement.

The category of rarity determines the rarity score of an item. Scoring, from least to most, according to category is: seasonal rare < limited rare < rare < ultra rare.

The item's price and level is also factored into its rarity score to prevent players from artificially boosting their rarity scores by purchasing a ton of cheap, low-level items. Overall, the rarity category contributes more to the rarity score than cost and level.

An official formula for determining Rarity Score has not been released.