Stoneforge vs Hushwing

[The Fluff]

Hi, for example an opponent cast a Stoneforge Mystic. Can I cast a Hushwing Gryff in response to the sfm, so that the opponent cannot search for an equipment?

[Lucifer, Sapere Aude]

As long as the Mystic is on the stack yes. Once the Mystic resolve and her ability goes on the stack is too late already (only a "counter target ability" effect would work in that case)

[peteroupc]

An effect that keeps certain abilities from triggering, as Hushwing Gryff has, doesn't counter or otherwise affect any abilities already on the stack, even if they're enters-the battlefield abilities that triggered because a creature or other permanent entered the battlefield.

However, if you cast Hushwing Gryff in response to Stoneforge Mystic, that is, before Stoneforge Mystic enters the battlefield, Hushwing Gryff will get to resolve first (C.R. 117.7) so that its effect can keep Stoneforge Mystic's enters-the-battlefield ability from triggering.

[The Fluff]

thanks for the answers. All clear to me now.