I was in the void messing around, when i realized i should try to find out why i can cast Shadows Of The Dead twice sometimes, even when i don't kill a single enemy after casting. then it struck me, what if the clones have their own separate storage, like a backup? and i am fairly certain i have found this to be true. let me explain what happened:
i killed random mobs (up to maybe 6 or 7 enemies) and i cast SOTD. i did not fire my weapon once, and when i tried recasting it "power not ready".
i killed random mobs at 20+ at least and i cast SOTD. i did not fire my weapon once, and when i tried recasting it "power not ready".
then i thought, each time i casted there weren't any enemies around, so what if there was and my clones killed some?
sure enough, i kill random mobs, up to 15 or so enemies, and i cast SOTD. they killed 2 corrupted corpus before they died. i tried recasting it and sure enough, 2 corrupted corpus clones were created.
i have also tested this a bit more, watching the enemies they kill, and taking note of what they killed first (thankfully, only one heavy was on the end, which they killed first) and after killing the enemies in the room, i recasted it, and no corrupted heavy gunner appeared, just the other enemies. which means this separate store also overwrites itself.
i would really like some raw data to confirm this, even though the evidence is pretty significant, just so i can know for certain this is how it works.