Advanced format ruling
Sinister Serpent
Card effect (current official text)During your Standby Phase, if this card is in your GY: You can add it to your hand, also banish 1 "Sinister Serpent" from your GY during your opponent's next End Phase. You can only use this effect of "Sinister Serpent" once per turn.
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.