There are two types of in-game currency in Prince of Persia: The Lost Crown: Time Crystals and Xerxes Coins.
 
Time Crystals can be earned by completing in-game activities, such as defeating enemies or destroying environmental objects. They can be used to purchase items and upgrade your gear.
 
Xerxes Coins can be found on mount Qaf and purchased from the Magi Emporium. They can be used to upgrade your gear.