Discard Amadeus Arkham >>> Whenever target attacker you control stuns an exhausted defender this turn, search your deck for a location card, reveal it, put it into your hand, and shuffle your deck. Use this power only if Amadeus Arkham is in your hand.

My question is,

If my "Target Attacker" attacks for a second time during "this turn", is Amadeus's effect still active, or does the ability disapear after my "target attacker" concludes the attack during which Amadeus was played?

since it says this turn instead of this attack, i would think it would last all turn. good eye, i never noticed that.

edit: i could be wrong though, i'm sure togorian will clear it up soon, that guy knows everything

The target has to be an attacker when you play the effect, but the effect lasts "this turn". (Meaning yes, if you stun a second exhausted defender somehow, you'll get the effect again.)

Compare to Last Stand. The +10 DEF lasts for entire turn.

*Quickly tries to think if Revenge Squad (5-Drop Bizarro) / Morlocks is feasable...*

JinxM is correct