Advanced format ruling
Gravekeeper's Assailant
Card effect (current official text)When this card declares an attack while "Necrovalley" is on the field: You can target 1 face-up monster your opponent controls; change that target's battle position.
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.