Machina Fortress [machine][7 star][earth][2500/1600]
[effect]=You can discard Machine-Type monster(s) whose total Levels equal 8 or more to Special Summon this card from your hand or Graveyard. When this card is destroyed by battle and sent to the Graveyard, select and destroy 1 card your opponent controls. When this face-up card you control is targeted by an opponent's Effect Monster's effect, look at your opponent's hand and discard 1 card from their hand.
saw this in wikia
If "Machina Fortress" is targeted by an opponent's Effect Monster's effect, then you check your opponent's hand and discard one card when the opponent's Effect Monster's effect resolves, before doing anything else.[2]
Example: Your "Machina Fortress" is targeted by the effect of your opponent's "Brionac, Dragon of the Ice Barrier". When resolving the effect of "Brionac, Dragon of the Ice Barrier", first, apply the effect of "Machina Fortress" and discard one card from your opponent's hand. After that, "Machina Fortress" is returned to your hand by the effect of "Brionac, Dragon of the Ice Barrier".[2]
isit really true? i thought it needs to survive on the field or something to make yr opponent discard. yes im slow ><