I invite you to take a look at all the decklists of the event and you will see that they are all built around the same premise: Beat the mirror and the other big deck in the format
The vicious visage of Darkest Diabolos, Lord of the Lair holds no hint of compassion or mercy, not even for cards that have yet to be played his special ability lets you Tribute a DARK monster to interfere with your opponent's hand
He will be available at all times for duels until the player defeats him, at which point the player obtains "Slifer the Sky Dragon" and Strings no longer appears, with Gravekeeper Ishizu appearing in his place instead
The added utility of providing blockers to bolster your life total, while granting some cheeky exalted triggers
Its defining move, Vanishing Strike, required one Psychic energy, two Fighting energies, and one Colorless energy to activate