Rarity

Rarity and Quality are properties of Items, which are represented in-game by the color and name under the item's name and (in most cases) by a title prefixed to the item's name. An item can have only one rarity and quality, which is determined when the item is created and remains unchanged, except in rare circumstances.

Rarity and Quality are purely cosmetic properties, and have no effect on gameplay.

Rarity
Items with a higher rarity have a less frequent drop rate than items with a lower rarity. Ancient items are never dropped.

Items are currently classified under one of the six following categories, ordered from most common to least common: Common, Uncommon, Rare, Mythical, Arcana, Legendary, Ancient, and Immortal.

Arcana
Arcana is a special rarity added in the March 07, 2013 Patch, this rarity directly changes the appearance of the Hero, their mini-map icon, or their abilities. The only Arcana item so far is Fiery Soul of the Slayer.

Quality
The quality of an item can be determined by its prefix.

Normal
Normal items are any item that has no denoted quality. They have no prefix.

Strange
Strange items have the capability of upgrading its own prefix, based on tracking a count of a specific in-game event. Strange items are obtained from opening hero-specific Treasure Chests.

Unusual
Unusual items have a special particle effect. To date, only couriers can have unusual quality. Unusual couriers are found in Treasure Chests at an approximately 1-2% chance.

Tournament
Tournament is a special prefix rarity on an item, such as Strange, there is no attached particle effect, just like the other usual item, but has been used in the tournament event.