Advanced format ruling
Royal Keeper
Card effect (current official text)Once per turn, you can flip this card into face-down Defense Position. When this card is flipped face-up, it gains 300 ATK and DEF until the end of the turn. (If attacked, this effect resolves after damage calculation.)
Current rulings for this card are maintained by Konami.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Advanced forum — sourced change requests get reviewed.