Upgrade Rarity

[Legionairie(BR)]

Is there anyway to increase the rarity from an item from common to uncommon ?

[Peredur]

To uncommon, no, as it doesn't exist. :p

But you can add a magic stat to a normal item to make it a magic item. Then add a rare stat to make it a rare item. Then add epic stats to make it an epic item.
You can also add a legendary effect to make it a legendary normal/magic/rare/epic item.

You can do pretty much anything with the help of the Blacksmith.
But you need to unlock the Blacksmith, have the ressources and don't miss the arrow at the end of the options displayed showing there are more options.