Some of the rewards available in the various difficulties include Orange Gear, Gold, Armory 16 Orb Fragments, and Iso-8 Blue materials. Also, there are two types of rewards that will be exclusive to each of the Sagas and a third reward type that is very rare. They are:

Awakened Abilities
Horseman Costumes
Iso-8 Blue Level 5 Ions & Crystals

Additionally, Apocalypse Shards and Red Stars can be obtained by completing Apocalypse's Saga.