Path of Exile is a great choice, totally free to play game. There are no cosmic requirements, and thanks to the pleasing graphic design it takes you to your climate. The game is easy and fun, not limited to killing monsters as in the paid Diablo 3. The most fun is to personalize the items into their character, the appropriate distribution of points on the skill tree (and the option is quite a lot). What allows you to create a character according to your idea. PoE Orbs are used for these, they are balls that affect the object on which they are used.
Some modify the quality of the item, others add to its magical qualities. The orbs have long since had many Orbs of Alchemy, Orbs of Scouring, Chaos Orbs, Divine Orb, Ancient Orb, Mirror of Calandra and the most popular Exalted Orb. The topic of the trade has been resolved very well, again in opposition to Diablo 3 (where trade is forbidden and impossible to make the official route).
PoE Orbs are also currency, but it is not a currency. Because PoE Orbs have properties, they are the objects that they use. So the currency has its value. There are two types of orbs, Exalted Orbs and Chaos Orbs.
Developers second to play so much has added to us recently released The Fall of Oriath.