You can target 1 LIGHT or DARK monster in either GY; banish it, and if you do, Special Summon this card from your hand. This is a Quick Effect if your opponent controls a monster. If this card is sent from the field to the GY: You can target 1 Special Summoned monster your opponent controls; send it to the GY. You can only use each effect of "Bystial Druiswurm" once per turn.
