[RaxleMF]

Thanks for the suggestion!

I had this thought too, except I didn't think of starting with /cleartarget, which fixes the issue I had. This would redundantly focus my Effigy every time I hit my Agony button, but I suppose there's no harm in it as long as I keep the /targetlasttarget at the end.

Edit: So the macro you suggested didn't work exactly as I had hoped, but I tweaked it a bit and now it's perfect. For reference, here's what I ended up with:

#showtooltip
/cast [mod:alt,@focus][] Agony
/stopmacro [@focus,exists]
/cleartarget
/targetexact Soul Effigy
/focus [exists]
/targetlasttarget [noexists]

This will just cast Agony as normal if my Soul Effigy isn't out. If it's out, it will swap to it and focus it if I don't have a focus already. With the original, I had some issues with my target dropping when I didn't want it to if my Soul Effigy was out and focused.