They were among the first Magic stories I got to read growing up and gave me a deeper love for the game's lore
It means the total number of cards in both you and your opponent's security stacks
For example, the Blend Energy card above shows 4 unique Energy types (Psychic, Fire, Grass, and Dark) behind a Colorless Energy symbol, indicating its ability to provide Energy of any of those types
It hasn't been long since the game's release, but it's not exactly a surprise to see this mod arrive so quickly, given the natural connection between the two
A great example of this strategy is the Toxtricity card from the Darkness Ablaze expansion
Each set will contain over 170 cards focusing on the 156 Pokemon of Unova, including rare illustrations and ex cards