J-Rulers are cards that take form from a certain Ruler, bestowing it with powerful abilities.
- J-Rulers are placed on the Field after being flipped over from its Ruler side, and may participate in Battles.
- A J-Ruler has separate Abilities from its other side.
- When a J-Rulers that has 0 DEF or less is destroyed, it doesn't go to the graveyard, it is sent back to the Ruler Area, keeping the J-Ruler side up. The J-Ruler then loses all its abilities and its ATK and DEF. (It may however still Rest and call Magic Stones)
- This is referred to as an "Astral Ruler".
- J-Rulers can't be targeted by Spells or Abilities that target a Resonator, but can be targeted by cards that choose a "J/Resonator".
- J-Rulers cannot attack or use activated abilities with included in required action the turn it was flipped from [Judgment] / [J-Activate]. (Unless the J-Ruler has Swiftness)
- During the Main Phase, a J-Ruler may be Rested to call the top of the Magic Stone Deck into your Magic Stone Area.
- A J-Ruler in the Ruler Area cannot be targeted with [Addition: J-ruler] or [Addition: J/resonator] cards.
- For a list of J-Rulers, see here.