I just realized you can use this on incorporeal creatures which is a bit odd. It seems useless at first but you could combine with Malock's torment to apply some direct damage (and maybe the new warlock can use it to help her burns get on incorporeal creatures which are otherwise very hard to burn)
It's not a big deal but it's a weird oversight. Or at least a change in policy to be less restrictive compared to say force hold which cannot target incorporeal creatures and is also useless on them.
And why not let us target conjurations? A rusty battle forge makes tons of sense and doesn't seem abusive in any way.