Oh! Use the "For each object" (it is under system)
So basic code will look like:
For Each Enemy
Enemy is close to player (whatever event you are using)
Enemy Attack
Sleipnir, the horse of Odin...
*edit*
Nevermind, I see ow you have this setup. You have a left and right detector for each skeleton's side, so that doesn't work.
I will get back to this, have to get cracking on my final... ><
Oh, for the skeleton's attack animation, one thing I do that isn't the "proper" way, but works, is to use the biggest animation frame as the template for each animation's size. In other words, make your largest animation frame a solid blue, then copy it for each other animation you have. Paste the other animations over that template, then they are all the same shape when you paste them into construct. Then delete the blue stuff but keep them all the same size. Use numpad 5 to center all the hotspots, and VOILA! (does that makes any sense?)
BTW looks like it'll be cool. My first thought was METROID! then I saw her jump. METROID! LOL
*edit AGAIN*
Didn't see Ashley's post. Follow his orders. He is teh smarts one.