Its rooted in Saussures semiotics, and its a part of literary critical theory that is well worth a dive into if youre interested
After this phase, there is an additional combat phase
Effects that remove all damage from a permanent (such as regeneration) will still remove damage from Ancient Adamantoise
So, a Ruby/Sapphire card that provides an ink ramp (a Sapphire hallmark) can be placed in a Ruby deck, providing more options and versatility
The Amber and Amethyst deck is for players who like having a lot of characters out at one time, while the Ruby and Emerald deck comes with a dash of control and counter abilities, meant to frustrate opponents as much as possible
These are filled to the brim with effect-granting songs, as well as an army of characters that can quickly Shift onto the board and sing them for free (Cinderella's a typical culprit)