Hmmm....yeah I think I'll just make a doodad key item, I want it to open a gate instead of a normal door anyway, so that way it won't end up in your inventory (you can't edit it out of your inventory once obtained unless you open a door).
I can just make it play the animation once it enters, looking as if it falls down, make a little bounce and time the sound right when it bounces.
I don't think I'm gonna use hammersprite for this, though, I've heard many people have issues with it. I'm just gonna do it manually I think.
Thank you!