Advanced format ruling
Book of Eclipse
Card effect (current official text)Change all face-up monsters on the field to face-down Defense Position. During the End Phase of this turn, change as many face-down Defense Position monsters your opponent controls as possible to face-up Defense Position, then your opponent draws cards equal to the number of monsters changed face-up by this effect.
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.