Olym is a family that is based on Greek mythology, hence all characters in this family are Greek deities. While other Grandwalker families didn't get much exposition to their personalities and backstory, Olym's flavor text speaks much of their Grandwalkers' stories and relationships, most of these stories being by-the-book adaptations of their actual tales on real Greek mythos.
In the card lore of the Grand Advent Saga, Olym's Grandwalkers allied with Lolo and Alex's forces in a war of defense against the Egytian legions' invasion of Grand-Lolo. However, after Egyt's invasions were successfully repelled, Olym's ruler and supreme deity Zeus, who previously merged with Lolo to become Zeus-Lolo in a desperate attempt to vanquish Ra, declared war on the entire Divine World and desired to unify and rule the universe with an iron fist. With Olym becoming an villainous force in the Ultra Advent Saga, Olym's leadership and armies became divided into two factions: loyalists who fought alongside Zeus-Lolo and defectors who joined Alex. After Zeus-Lolo was separated back into his original components and Dionysus, the wire-puller behind the everything that transpired, was defeated, Zeus went into self-exile and his right-hand Hermes took the position as Olym's acting supreme deity and leader.