If a Spell/Trap(s) you control leaves the field because of an opponent's card effect and is sent to the GY or banished: You can Special Summon this card from the GY (if it was there when that Spell/Trap left the field) or hand (even if not), then you can Set 1 of your Spells/Traps that is banished or is in your GY to your Spell & Trap Zone. If Summoned this way, banish it when it leaves the field. You can only use this effect of "Mana Dragon Zirnitron" once per turn.