BM-4 Blast Spider

Once per turn: You can target 1 DARK Machine monster you control and 1 face-up card your opponent controls; destroy them. If a monster you control that was originally a DARK Machine destroys an opponent's monster(s) by battle or card effect and sends it to the GY: You can inflict damage to your opponent equal to half the original ATK of 1 of those monster(s) destroyed and sent to the GY. You can only use this effect of "BM-4 Blast Spider" once per turn.