Rift
There are 4 (four) types of Rifts. You will be able to battle to 5 (five) times a day in each of them:
Equipment Material Rift
Provides Refining Stones in large quantities to improve equipments.
Skill Material Rift
Provides Skill Books in large quantities to improve the hero's skills.
Gold Rift
Provides large amount of Gold.
EXP Rift
Provides large amount of EXP.