"Mekk-Knight", known as "Jack-Knights" (ジャックナイツ, Jakkunaitsu) in the OCG, is an archetype of LIGHTmonsters debuting in Extreme Force. The archetype is both related to and supported by the "World Legacy" archetype. All members of this archetype are Psychic monsters, except for their Extra Deck monsters.
All "Mekk-Knight" Main Deck monsters (except "Mekk-Knight Avram") share the following effect:
"If 2 or more cards are in the same column, you can Special Summon this card (from your hand) to that column."
The deck itself relies on Special Summoning, doing so in orderly fashion to take advantage of their column-based effects. They can also modify their formation to fit almost every situation at will, mostly to enable the negation effects of "World Legacy Key", "World Legacy Whispers", and "World Legacy's Secret". "Mekk-Knight Blue Sky" and "Mekk-Knight Purple Nightfall" is the most important monsters within the deck due to their search effects, and together with "World Legacy's Memory", allows them to keep Summoning monsters without pause and use them to either Link Summoning, or straight-up inflicting damage. Due to how this deck's mechanic works, this deck can performs better when going second.
Most iteration of the deck also employs "Aleister the Invoker" (along with "Invocation", "Magical Meltdown", and the "Invoked" Fusion Monsters), not only to increase their offensive power but also to better safeguarding their field presence (courtesy of "Invoked Mechaba"). Other than that, this deck's core components (consisting of "Blue Sky", "Purple Nightfall", and "Indigo Eclipse") can also be used in other decks that needs more swarming and offensive power.