Advanced format ruling
Ground Spider
Card effect (current official text)Once per turn, if you control this face-up Defense Position monster when your opponent Normal or Special Summons a monster(s), you can change that monster(s) to Defense 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.