Gigantic Force is a transcendental skill that increases physical strength. It is the basis for the divine magic hoti kubera, which makes selected body parts stronger with a golden light. However, this transcendental affects the entire body, and changes hair and eye color to gold in addition to the golden swirls of light around the user.
Unlike the divine magic hoti kubera, this is a passive skill as it automatically activates at nighttime, from the Time of Earth (dusk) until the Time of Resurrection (dawn). In a space or dimension where day and night are not differentiated, it is always considered night.
This skill is the reason God Kubera created the Golden Knight. Of course, he is now able to control his power at night even without the item.
There are many other transcendental skills that similarly strengthen the user, so this skill is not considered unique.
When God Kubera appears during Leez's passage through the water channel, this skill is active the entire time, likely because the water channel is in a separate dimension with no night or day.