One was a good brother, and due to certain circumstances, the other grew up corrupted. In this case, "Castor" became infected to save his brother from "Gishki Psychelone".
Both are twin brothers of the Gemini constellation.
Like Saga on the Hades Chapter, "Castor" is on the side of the Enemy and wears a dark version of his armor.
Kanon was able to make peace with his brother, and like him, "Pollux" is able to return his brother to sanity.
This card's effect is based on its Gemini theme; usually, every player can only have 1 Normal Summon or Set per turn, but this card allow another Normal Summon or Set. This card can give twin Normal Summons or Sets.
This card appears in the artwork of "Constellar Star Cradle" and "Constellar Meteor".
So far, any card featuring either "Castor" or "Pollux", besides their own, feature both of them.