It is my opponent's turn. He has an Elvish Mystic on the field (1/1). He declares his Elvish Mystic as an attacker, then activates his Ghor-Clan Rampager's Bloodrush ability from his hand, with the target being his attacking Elvish Mystic.
I have a Wring Flesh in my hand and the mana to cast it. I target his Elvish Mystic.
If my instant does not take precedence, Elvish Mystic becomes a 5/5 from Bloodrush, then drops to a 2/4 from Wring Flesh.
If my instant takes precedence, this means the Elvish Mystic ends up in the graveyard.
What happens to the Ghor-Clan Rampager? Does Ghor-Clan Rampager still cast Bloodrush (on an invalid target) and get discarded, or does it remain in his hand without activating?